Rainwater and Greywater as Alternative Water Resources: Public Perception and Acceptability. Case Study in Twelve Countries in the World

The aim of the paper was to identify factors that influence the public perception of the possibility of replacing tap water with rainwater or greywater. In order to check whether a geographical location and water resources of a region affect the public's attitude toward alternative water systems, the surveys were carried out among respondents from twelve countries. The surveys identified the level of awareness among respondents about their country's water resources, ways to save water at home, and their attitudes to rainwater and greywater as additional sources of water in a building. The results showed that only 39% of respondents would not be afraid to use treated greywater in their household. The situation was better in case of replacement of tap water with rainwater, where more than 54% of the respondents were not concerned. The use of alternative sources of water for body washing and cleaning works was the biggest concern among the respondents. In case of greywater recycling, this was indicated by 56% (personal hygiene) and 34% (cleaning works) of respondents. People in the countries with low water resources view alternative water sources more favourably. They are also more aware of, and more likely to accept the use of rainwater or greywater even in uses where they will come into contact with the human body. The research also showed that for more than 3/4 of respondents, funding to install these systems would encourage their use in their household.


Introduction
The construction sector is one of the largest water consumers in the world (Mannan and Al-Ghamdi 2020).Residential buildings account for around 12% of global water consumption (UN 2021), and in some countries it is up to 30% (Ritchie and Roser 2018).One needs to consider that modern water management models should be introduced in this sector.This is relevant as the projected increase in the world population to 9.7 billion by 2050 (UN 2019) could result in an increase in global water demand of more than 50% (WWAP 2015).
There are many water saving opportunities at building scale, ranging from people's environmentally-friendly behaviour, through the use of water-use reduction devices, to alternative water sources (Pagano et al. 2021).Decentralised alternative water systems, including rainwater harvesting systems (RWHS) and greywater recycling systems (GWRS), are increasingly seen as solutions which bring not only environmental but also financial and social benefits (Ferreira et al. 2023;de Sá Silva et al. 2022).It is worth emphasizing that greywater is not only a valuable source of water, but also energy (Piotrowska and Słyś 2023;Pochwat et al. 2020).
Many researchers have focused on the financial and technical aspects of these systems, which mainly depend on a type of a building and a geographical location (Pacheco and Alves 2023;Moniruzzaman and Imteaz 2017;Amos et al. 2016).In the literature, some references are made on this topic to single-family (Słyś 2009) and multifamily buildings (Bashar et al. 2018;Stephan and Stephan 2017), public buildings (Chen et al. 2021;Karim et al. 2021) and university facilities (Cardoso et al. 2020;Stec and Zeleňáková 2019).In these facilities, rainwater and greywater are mainly used for toilet flushing, laundry, cleaning and irrigation (Khan et al. 2021;Imteaz et al. 2012).
Wider uptake of alternative technologies always faces many problems.Technical, financial, legal and social barriers are among the biggest obstacles.In case of unconventional water sources, the social factor is decisive (Dobbie et al. 2016).In spite of technological progress, which has significantly improved the treatment of waste water (Çiftçioğlu-Gözüaçık et al. 2023), the public remains largely sceptical about the use of rainwater and greywater as centralised and decentralised water sources (Fielding et al. 2018).The lack of population acceptance for the implementation of these systems involves a perception of health risk and low financial reward (Campisano et al. 2017).
The way howrainwater or greywater are used also affects acceptance or lack of it, and the perception of the risks associated with it.The use of recovered water for activities during which it will come into contact with the human body, such as household cleaning, laundry and car washing, is of great concern (Fielding et al. 2015).Some people may accept the use of greywater for toilet flushing, but not for washing or drinking (Jamrah and Ayyash 2008).The situation is similar when it comes to the choice of alternative water sources.One may see rainwater safer than greywater, as the second one may contain gastrointestinal pathogens and small amounts of urine and faecal material (Leong et al. 2017).
When analyzing the studies published, it was noticed that the socio-cultural factor was very important and for many people it could be decisive in choosing an additional water source in their household.Some studies indicate that low public awareness is the key issue in this topic, most often caused by the lack of educational campaigns (Dolnicar et al. 2010).Some examples of this have already been seen around the world where public opposition delayed, and in some cases blocked, the implementation of alternative water systems (Fielding et al. 2018).Public opinion surveys were carried out mainly in Australia (Delaney and Fam 2015), the United States (Garcia-Cuerva et al. 2016), Asian countries, such a China and India (Vasudevan and Natarajan 2021;Gu et al. 2015), and in Arabic countries (Chfadi et al. 2021).There is a small number of studies in European countries (Egyir et al. 2016;Domènech and Saurí 2010).
Lack of public acceptance of the use of alternative water sources in buildings may be difficult to understand, especially in countries where water shortages occur.It results from current climate conditions, or projected climate change.According to the European Commission data, at least 11% of Europeans are affected by water scarcity and only one billion m 3 of treated urban wastewater is reused annually.It might seem like a lot, but six times more treated water could be reused than current levels (EU 2023).Despite the fact that the importance of eco-friendly behaviour and action is increasingly recognised by the society, there is still a lack of research to learn about public opinion of these resources.In order to check whether the climate, geographical location and water resources of a region affect public opinion toward alternative water sources, a survey was carried out in twelve selected countries around the world.This survey identified the level of awareness among respondents about their country's water resources, ways to save water at home, and their attitudes to rainwater and greywater as additional sources of water in a building.Not only the comparative analysis of opinions of different societies is novel compared to the published research, but also the inclusion in a single survey of issues relating to the two most widely used non-conventional water systems (IWA 2015).It should be stressed that these studies were both of a scientific and practical nature.They can be the starting point for the development of appropriate educational tools and awareness-raising campaigns in this area.The conclusions of these studies can also be a valuable guide for policy makers, social and environmental organisations, as well as other researchers who focus their efforts on more sustainable water management.

Survey Design
The first and most important step to prepare a survey is to clarify what we want to learn from it.It is a mistake to take a holistic approach and ask a large number of questions to get as much information as possible (Jones et al. 2013).This does not work because asking too many irrelevant or inconsistent questions limits the percentage of responses, and thus reduces the strength of the survey (Edwards et al. 2009).Taking this into account, the study was planned according to the steps shown in Fig. 1.
The questionnaire was divided into two main parts.The first one consisted of four questions (Q1-Q4, Appendix A, Table 1) designed to characterise the research group.Respondents were asked about their age, gender, education and place of living.The second part of the questionnaire, containing nine questions (Q5-Q13, Appendix A, Table 1), concerned water conservation issues and the possibility of implementing unconventional water systems in the respondents' households.

Target Population and Survey Distribution
The survey research was conducted in twelve countries, eight European and four outside Europe, and the vast majority of questionnaires (87% of all surveys) were completed online.The online method allowed conductingsurveys on a larger research group and obtaining a lot of valuable information.One-on-one surveys were expensive and very timeconsuming (Jones et al. 2013), especially in the case of research conducting in many countries.An online questionnaire was prepared in Google Forms in Polish (research conducted in Poland) and English (research conducted in other eleven countries) and a link with questionnaire was sent via e-mail to the respondents in 2019 and 2021.A similar test method was chosen by (Kordana-Obuch et al. 2021).

Data Analysis
The results of the survey were analysed using the Statistical Package for Social Sciences, which is a frequently used tool for the statistical analysis (Okagbue et al. 2021).The significance of differences in the respondents' answers was determined using the Chi-square (χ 2 ) test of independence, also known as the Pearson test.It is one of the most commonly used statistical significance tests (Turhan 2020).The Eq. ( 1) was used to calculate this parameter.In these studies, the significance level (p) was assumed not higher than 0.05, similar to the research conducted by (Garcia-Cuerva et al. 2016).
where: O i -observed value, E i -expected value.

Case Study
The survey was conducted for twelve countries: Poland, The Czech Republic, Slovakia, Hungary, Spain, Portugal, Italy, Sweden, Turkey, Iraq, Egypt and Brazil.The study focused mainly on European countries since unconventional water systems are rarely used on this continent.In recent years, there has been an increase in interest in these systems, but it is still at an unsatisfactory level.This problem is important and requires a decisive action as many regions of Europe have very poor water resources.The aim of the study was also to examine the impact of the climatic conditions of a region on respondents' responses, and therefore there were selected the countries which could be divided into those with small (up to 5 000 m 3 /person/year), medium (from 5 000 to 10 000 m 3 /person/year) or large (above 10 000 m 3 /person/year) water resources.Table 2 provides general information in this area.When selecting countries for the study, the possibility of water shortages was also taken into account.According to the World Resources Institute, 1/4 of the world population faces "extremely high" levels of baseline water stress and 44 countries face "high" levels of stress (WRI 2021).The Institute's forecasts also show that the situation will have deteriorated by 2040 in many regions, including the countries under consideration.Table 3 shows current data and projected changes in water crises in the countries under examination.

General Characteristics of Survey Respondents
Two thousand nine hundred thirty-one surveys were sent, and 1,200 questionnaires were returned and correctly completed.This represents approximately 41% of the total number of questionnaires distributed.This result can be considered average.For example, Mu'azu et al. (2020) in similar studies, have obtained a 64.3% response rate.In turn, in the survey conducted by Egyir et al. (2016) the percentage of responses was significantly lower, ranging from 19 to 28%.The detailed data obtained in this study is shown in Table 4.The (1) percentage of returned questionnaires was higher and amounted to 46%, but about 5% were not correctly completed and it was decided to reject them.
The results of the survey were analysed by comparing answers from respondents from each country and with a division into three groups depending on the country's water resources (up to 5 000 m 3 /person/year, 5 000 to 10 000 m 3 /person/year, and above 10 000 m 3 /person/year).The largest number of respondents came from the countries where water resources were less than 5 000 m 3 per person per year (59%).The fewest respondents came from the countries where water resources were between 5 000 and 10 000 m 3 /person/year.These were Portugal (9%) and Slovakia (9%).Other respondents lived in the countries where water resources exceeded 10 000 m 3 /person/year, i.e.Hungary (9%), Sweden (8%) and Brazil (5%).
Among those surveyed, there were slightly more men (51%) and the proportion of women was 49%.The statistical analysis did not reveal significant differences in gender between groups divided according to water resources (χ 2 = 0.85, p = 0.653).There were also no significant differences in the gender distribution between the different countries (χ 2 = 5.00, p = 0.931).The largest numbers of respondents were between 35 and 44 years old (35%) and between 25 and 34 years (28%).In this case, statistically significant differences between the groups divided according to water resources were also not observed (χ 2 = 12.50, p = 0.406).The age group distribution in each country was similar to that in the general population (all respondents) (Fig. 2).The statistical analysis, which did not take data gaps into account, did not show statistically significant age differences between groups divided according to age (χ 2 = 38.70,p = 0.953).
The higher percentage of respondents had tertiary education (73%), 26% of respondents had up to secondary education, and a small percentage of respondents (1%) had up to primary education.The statistical analysis did not show significant differences in the level of education between groups divided according to water resources (χ 2 = 5.40, p = 0.249).
Most of the respondents lived in urban areas (64%), while others lived in the rural areas (36%).The analysis carried out in this case also did not show statistically significant differences in the place of residence, both between groups divided according to water resources (χ 2 = 0.33, p = 0.847) and the country of origin (Fig. 3).
In conclusion, it can be stated that the groups of respondents from each country were similar in terms of gender, age, education and place of living.

Perceptions of Water Conservation
The most important part of the questionnaire defined the respondents' scope of knowledge about water resources in their country and the possibilities of their protection through the use of unconventional sources, such as rainwater and greywater.
More than 50% of the respondents said that there was a problem with drinking water scarcity in their country (answers to the question Q5).The respondents (63%) from countries with water resources below 5 000 m 3 /person/year were most likely to see this, less frequently the respondents (39%) from regions with medium (Portugal, Slovakia) and large (26%) fresh water resources (Hungary, Sweden and Brazil).These differences were statistically significant (χ 2 = 60.87,p < 0.001).Most frequently, people from Iraq (88%), Turkey (85%), Egypt (85%) and Spain (78%) indicated a problem of drinking water scarcity (Fig. 4).On the other hand, the fewest people who indicated this problem came from Sweden (16%), Slovakia (24%) and Brazil (27%).The analysis of the Chi-square test showed that these differences were statistically significant (χ 2 = 134.22,p < 0.001).
An important issue showing the respondents' attitude to the protection of water resources was the question (Q6) of the reasons for saving water at home.A multiple choice was possible out of the answers: water resources protection and tap water bill reduction.The desire to protect water resources was a little more likely to be given as a reason to save water (63% of the total).This reason was most frequently chosen (66%) by the respondents living in the countries with low (The Czech Republic, Poland, Italy, Spain, Turkey, Egypt and Iraq) and medium (62%) water resources (Portugal and Slovakia), slightly less frequently (56%) by the respondents from countries where water resources are high (Hungary, Sweden and Brazil).However, this difference is not statistically significant (χ 2 = 4.83, p = 0.089).Less frequently, the reason given for saving water was to reduce bills.This reason was most frequently indicated by the respondents living in the countries where water resources are high (62%), less frequently by people from countries with medium (54%) and low (55%) water resources.A statistical analysis using the Chi-square test in this case showed that these differences were statistically insignificant (χ 2 = 2.63, p = 0.269).
A large majority of respondents (more than 80%) claimed that water was being saved in their households (Q7).The respondents answered similarly, e.g. in the studies by Garcia-Cuerva et al. (2016) and Hasan et al. (2021).In this study the most common ways to save water were turning off the tap when brushing teeth (72% of the total), checking and repairing dripping taps (61%), taking showers instead of baths (52%).A less common method of saving water was to use the washing machine only with a full load (51%) and washing dishes in a dishwasher (50%).Both of these methods of saving were most frequently chosen in the countries with low levels of water resources, and the least frequently by respondents from the countries with high levels of water resources (Hungary, Sweden and Brazil).The differences between the groups were statistically significant and the significance levels were 0.024 and 0.015, respectively.When analysing responses in particular countries, it was noted that in three of them a significant proportion of respondents did not save water.These were the Brazilians (30%), the Slovaks (26%) and the Czechs (22%).
Sixty-four percent of the respondents were aware that at least half of the water they used could be replaced with rainwater and greywater (Q8).Respondents from the countries with low (68%) and medium (64%) water resources were most likely to be aware of this, less frequently from countries with high water resources (54%).The statistical analysis showed that these differences in the distribution of responses between the studied groups were statistically significant (χ 2 = 8.11, p = 0.017).Most frequently respondents knew that more than half of the water consumed per day could be replaced by lower quality water.The lowest percentages of people aware of this were from Brazil (30%), Slovakia (49%), Hungary (46%), the Czech Republic (48%) and Poland (58%).The Pearson's test showed that these differences were statistically significant (p < 0.001).

Perceptions of Rainwater Harvesting Systems and Greywater Recycling Systems
The main purpose of the survey was to find out the opinion of societies about alternative water systems, which can be determined from the answers to the last 5 questions of the questionnaire.Two questions (Q9 and Q10) were related to the concerns of using greywater and rainwater for toilet flushing, laundry, cleaning works, car washing and watering.In the next two questions (Q11 and Q12), the respondents expressed their willingness to use the rainwater harvesting system and greywater recycling systems in their households.If they were not interested in these systems, they could choose the reason for this: hygiene considerations, high installation costs, or both.The last question (Q13) concerned co-financing for the installation of the systems in homes.
Thirty-nine percent of the respondents did not have any concerns about using greywater in their houses.Most frequently (43%) these were people from the countries with low water resources (The Czech Republic, Poland, Italy, Spain, Turkey, Egypt and Iraq), less frequently among respondents from the countries (Portugal and Slovakia) with medium (33%) and high (32%) water resources (Hungary, Sweden and Brazil).These differences are statistically significant (χ 2 = 6.86, p = 0.032).The use of greywater for washing (56%) and household cleaning (34%) was the biggest concern.It was lower for garden watering (22% of people questioned had concerns), toilet flushing (21%) and car washing (13%).Only for car washing there were no statistically significant differences between the groups under the study (χ 2 = 1.21, p = 0.547).In other cases, these differences are statistically significant (p < 0.05).In all tested greywater uses, the most concerns were found among those from the countries with high levels of water resources, and the least from countries with water resources below 5000 m 3 /person/year (Fig. 5).
Respondents were most concerned about the use of treated greywater for washing in Hungary (76%), Slovakia (71%), Brazil (67%) and the Czech Republic (65%).The lowest percentage of people who had concerns about using greywater for this purpose came from Iraq (39%), Egypt (40%) and Spain (44%).These differences are statistically significant (χ 2 = 30.48,p = 0.001).These are the countries with low water resources and the acceptance of greywater for washing at the level of about 60% is caused by the perceived problem with the availability of these resources.Very similar results were obtained by Pham et al. (2011) who conducted research on public attitudes towards recycled water in Sydney.These studies showed that 97% of the local respondents were aware of persisting water shortage problem and 61% were not concerned about using greywater for clothes washing.Over 70% of respondents were willing to use treated greywater for toilet flushing, garden watering and cars washing (Pham et al. 2011).In turn, Van der Hoek et al. (1999) found that as many as 80% and 97% of Amsterdam's residents supported greywater reuse for washing and toilet flushing, respectively.
Significant concerns about the use of greywater for garden watering were found among respondents from Hungary (43%), Slovakia (31%), Brazil (30%) and Sweden (30%).In contrast, a smaller percentage of people from Iraq (9%), Egypt (10%), and Turkey (11%) were concerned about using greywater for garden watering, suggesting that more people in these populations may be willing to use greywater for this purpose.
These differences are statistically significant (p < 0.001).The situation with regard to the use of treated greywater for household cleaning was similar.Most frequently there were no concerns among the Iraqis (61%), the Spaniards (56%), the Portuguese (51%) and the Egyptians (50%).The Chi-square test showed that the differences were statistically significant (p < 0.001) (Fig. 6).
Many more respondents had no concern about using rainwater in their households (54%) compared to greywater.There were no significant differences in the responses between the groups of countries classified in terms of water resources (χ 2 = 2.95, p = 0.229).Respondents most frequently were concerned about the use of such water for washing (43%) and household cleaning (21%), less frequently for toilet flushing (14%), car washing (6%) or garden watering (3%).Sheikh (2020) reached similar conclusions, stating that over 65% of respondents accepted rainwater for outdoor usage (watering the garden, washing the car), and only a few would like to use it for washing or cooking.Also Egyir et al. (2016) found that rainwater for domestic purposes was most readily used for toilet flushing, gardening and car washing.In turn, Mankad et al. (2012) showed that 96% of Australian householders reported using their tank water for outdoor use alone.The research that was conducted in the UK has also shown positivity towards the rainwater harvesting systems.Ward et al. (2013) found that overall acceptance of RWHS in this country was high, and was positive for a wide range of uses.For example, 93% of householders would consider using rainwater to flush the toilets.
When analysing results for each country, it was observed that the concerns about the use of rainwater for clothes washing were mainly reported by the Brazilians (60%), the Poles (58%), the Slovaks (56%) and the Hungarians (53%).A much lower proportion of people (around 30%) from other countries indicated the same.These differences are statistically significant (χ 2 = 27.29,p = 0.004).Respondents were more favourable towards the use of rainwater for household cleaning in Iraq (70%), Spain (67%), Portugal (67%), Italy (67%), Turkey (66%) and Sweden (62%).The lowest percentage of people with no concerns about the use of rainwater came from countries such as: Slovakia (31%), Brazil (40%), Poland (40%), the Czech Republic (42%) and Hungary (47%).The statistical analysis performed using the Chi-square test showed that these differences were statistically significant (p < 0.001).The results of the studies in this area are presented in Fig. 7.The use of rainwater for garden watering and car washing were of the least concern among the respondents.No statistically significant differences were found for other factors (p ≥ 0.05).The watering of gardens was also the most accepted use in Malaysia (81%), UK (89%) and Mexico (80%) (Asmuni et al. 2016;Ward et al. 2013;Fuentes-Galván et al. 2018).
Based on the responses to Q9 and Q10, it can be concluded that the respondents have fewer concerns about the use of rainwater than greywater in their households.Also, López-Ruiz et al. ( 2021) emphasized that recycled water was the least acceptable option for alternative sources of water, behind both rainwater collection and desalination.
Two further questions (Q11 and Q12) addressed the feasibility of implementing RWHS and GWRS in the households surveyed.Most respondents (57%) expressed their willingness to use the RWHS.The distribution of responses was not found to be significantly linked to the country's water resources (χ 2 = 5.38, p = 0.068).The main reasons for a lack of willingness to use this system were: the increased costs (31%), less frequently hygiene considerations (23%).
When analysing the results of the study for each country individually, it was not found that the choice of increased investment as a reason for not applying a rainwater system was significantly statistically differentiated by the respondent's country of origin (χ 2 = 17.78, p = 0.087).However, it was observed that the indication of hygiene considerations as a reason for a lack of willingness to implement a RWHS was statistically significant (χ 2 = 21.05,p = 0.033).Most frequently this reason was chosen by the Slovaks (36%), the Poles (32%) and the Hungarians (31%).It was least frequently chosen by the respondents from Turkey (13%), Portugal (13%), Iraq (15%) and Egypt (15%).The distribution of affirmative responses expressing willingness to install a rainwater harvesting system is shown in Fig. 8.The differences between the countries studied were statistically significant (χ 2 = 27.55,p = 0.004).
In the case of greywater recycling systems, only 45% of all respondents would like to apply this solution in their household.In contrast with the RWHS, the water resources of the region affected the responses and these differences were statistically significant (χ 2 = 27.01,p < 0.001).Respondents from the countries where water resources were low (53%) and average (42%) were most likely to have such a desire, less frequently respondents from the countries with large water resources (27%).The main reason for a lack of willingness to use such a system were hygiene considerations (42%), less frequently increased investment (26%).More frequently, both reasons were chosen by people from the countries with high water resources, least frequently by respondents from low-resource countries, and the differences were statistically significant (p < 0.05).Scruggs et al. (2020) also found that people living in regions with water scarcity were more likely to water reuse, even for potable purposes.Although Mankad et al. (2015) emphasize that in most cases people accept recycled water for non-potable applications and not for human consumption.
When analysing the responses for each country, it was noted that, as for the RWHS, the choice of increased investment as a reason for not applying a system for the use of greywater was statistically significantly differentiated by the respondent's country of origin (χ 2 = 17.71, p = 0.088).However, it was found that the indication of hygiene considerations as a reason for a lack of willingness to install a GWRS was significantly differentiated by the country of residence of the respondents (χ 2 = 43.07,p < 0.001).Most frequently this reason was chosen by the Hungarians (62%), the Slovaks (58%), the Swedes (52%) and the Czechs (52%).It was least frequently chosen by respondents from Iraq (21%) and Egypt (23%).
Most frequently, a desire to use the GWRS was expressed by respondents from Egypt (65%), Iraq (64%) and Turkey (64%).It was least frequently chosen by respondents from Brazil (20%), Hungary (22%) and Slovakia (31%).These differences were statistically significant (χ 2 = 55.18,p < 0.001).Figure 8 shows the results of the studies in this area, together with the distribution of responses for a rainwater harvesting system.When analysing this data, one can see a trend in responses that show an increase in favour of the rainwater harvesting system rather than the greywater recycling system.This is particularly evident for countries with significant water resources, such as Brazil, Hungary, Sweden and Slovakia, where the differences in the "yes" responses for both systems were up to 20%.
When comparing the results of this research for both alternative systems, it was observed that in both cases these were the Brazilians, the Slovaks, the Czechs, the Poles and the Hungarians who had the greatest concerns.With the exception of the Czech Republic and Poland, these are countries with significant water resources, where water shortages do not occur or appear only periodically.This may indicate that the people of these countries are not convinced about unconventional water sources as they have not experienced a lack of water, and that environmental considerations, and the need to protect natural resources are not so important to them.The reason for the lack of disapproval and aversion to unconventional water sources in these countries may also be the lack of appropriate legal regulations and educational campaigns increasing the popularity of these systems.Abubakara and Mu'azub (2022) also emphasize that behavioural change campaigns are key to increase the use of alternative water sources and protect the dwindling freshwater resources.Takagi et al. (2019) found that acceptability of harvested rainwater was high among the public in Sri Lanka, and increased even further subsequent to the provision of information on quality, quantity and cost.The people who considered it unacceptable tended to change their attitude to acceptable, after provided such information.
It should be emphasized that residents of countries such as Iraq, Turkey, Egypt and Spain are more favourable toward alternative water sources as in many regions people suffer from a lack of water and recognise the need to take measures to reduce water consumption.They are also more aware and more likely to accept the use of rainwater or greywater even in uses where they will come into contact with the human body.This may be influenced by information and education campaigns and laws promoting, and in some cases mandating, the use of unconventional water systems, which have been amended over the years (Domènech and Saurí 2010).
In the final question, the respondents were asked about the issue of funding for the installation of alternative water systems.Most of them considered that such funding would encourage the use of RWHS and GWRS in their household (77%).Most of these (80%) came from countries with small (The Czech Republic, Poland, Italy, Spain, Turkey, Egypt and Iraq) and medium (76%) water resources per capita (Portugal and Slovakia).Respondents from countries where water resources are high: Hungary, Sweden and Brazil (68%) were less likely to be of this opinion.In the case of the latter, funding would not be sufficient to trigger the implementation of the RWHS or the GWRS as a large proportion of these people indicated that hygiene considerations were the greatest barrier for them.The analysis showed that these differences were statistically significant (χ 2 = 7.69, p = 0.021).The survey results for each country show that for the vast majority of respondents from Iraq (91%), Egypt (90%) and Turkey (87%) subsidies would provide a strong incentive to implement these schemes.The Chi-square test showed that these differences were statistically significant (χ 2 = 35.12,p < 0.001).The detailed results of the study are shown in Fig. 9. Financial support as a factor determining the acceptance of unconventional water systems were highlighted in other studies where respondents did not consider installation costs as a disadvantage because they were absent or negligible (Barthwal et al. 2013).
The study showed that for the vast majority of respondents funding to install these systems would encourage their use in their household.The need for a strategy offering financial incentives to the population, and thus preventing the implementation of water protection practices from being hampered was also underlined in research by dos Santos et al. (2020).A prime example of this is the city of Sant Cugat del Vallès in Spain, which made it compulsory to install RWHS in new homes, offering subsidies at the same time.The survey among the users of these systems showed that they could see the benefits of such solutions, both environmental and financial (Saurí and Garcia 2020).In turn, the research of Barthwal et al. (2013) showed that residents of Dehradun, India accepted rainwater as an alternative water source, but that the government needed to develop plans to support largescale implementation of the RWHS.These examples show how important the right actions and initiatives developed by government institutions are.

Summary
Unconventional water systems are becoming more and more popular not only among investors but also researchers.In their research, they mainly focus on technical, financial and social issues that arise from the use of rainwater harvesting systems and greywater recycling systems.In particular, the social issues may constitute the greatest barrier to largescale implementation of these systems.This was confirmed by the survey results reported in this paper.On the basis of these results, it was concluded that hygiene considerations were the largest problem in the implementation of alternative water sources, especially in the countries with significant water resources.The inhabitants of these regions do not recognise the need to conserve resources through the use of rainwater and greywater, as most of them have not experienced problems due to a lack of water.This position may also result from a lack of appropriate educational campaigns in these countries as only half of those surveyed were aware of the possibility of replacing tap water with rainwater or greywater.In contrast, respondents living in the regions with low water resources were more favourable toward these two alternative water sources and for them hygiene factors were not so important.This was not only determined by limited availability to fresh water, but also by the introduction in many countries of a sustainable water management strategy based on social campaigns, legislative changes and government subsidies.
For many respondents, the financial aspect was the reason why they were not interested in using a rainwater harvesting system or greywater recycling system.Nearly 80% of the respondents indicated funding as an incentive to install these systems in the household.The results of these studies show that offering subsidies or tax reductions to those who choose to implement the schemes concerned could be an important social factor in the implementation of sustainable water strategies.
This study focused on social issues related to decentralized water systems.Future studies should also include learning about the opinions of society about the use of treated greywater and rainwater supplied to buildings from central water systems implemented for the estate, a part or the entire city.This is an important issue as some people may perceive centrally treated greywater to be safer and less disgusting than those from individual systems.
It is worth pointing out that in order to make changes in communities, there is a need to conductintensive, effective environmental campaigns by the government and nongovernmental institutions, but also to carry out research to discover and understand the socio-technical barriers arising from the implementation of alternative water systems.Knowledge improvement about these systems would reduce the likelihood of rejection by society as often something new and unknown is perceived as risky.

Fig. 3
Fig. 3 Division of respondents according to their place of residence

Fig. 4 Fig. 6 3 Fig. 7
Fig. 4 Affirmative answers to the question about the problem of water deficits in the respondent's country

Table 1
List of questions included in the survey