The water quality of in storage containers (clay pots) may be impacted if it is directly or indirectly exposed to external factors such as temperature, wind, and dust. Household water quality is affected by the cleaning of water storage tanks and vessels. Water storage is globally observed and may reflect a lack of trust in the government-run water supply infrastructure. Water storage tanks can be cleaned manually with specialized mops or brooms, mechanical scrubbers, water jets, hoover cleaners, and special chemicals [20].

Several studies have investigated tank cleaning. Sule et al. [21] noted that inadequate hygiene methods and dubious source water contributed to a significant decline in the quality of stored water in Ilorin, Nigeria. In another study, a relationship was established between tank handling procedures in Zaria, Nigeria, and the quality of stored water [22]. In South Africa, houses were supplied by water tankers, so it was safer to clean the tank before each filling to ensure the quality of the water from tanker trucks and prevent the transfer of pollutants from the previous supply [23].

For this study, the physicochemical parameters pH, temperature, EC, TDS, turbidity, total hardness and its fractions, ammonia, chlorine, chloride, and Zn were tested. The pH of tap water and tank water samples (8.75 and 8.69, respectively) in this study was slightly higher than the pH value in another study which also used clay pots (7.9, 7.8, and 7.5, respectively) [24]. The pH increases after storage may be due to the drop in aqueous carbon dioxide (CO2) in the stored water since the clay pot is alkaline in nature, which increases the pH of water [25]. The pH of water is influenced by several factors, including the water source, the material of the water storage tank or vessel, temperature, mineral absorption, dust, amount of bacterial activity in the vessel, and amount of time the water is stored until usage [26]. The alkaline composition of clay is another advantage of clay waterpots. The correct pH balance is produced by the interaction between the alkaline clay and the acidity of the water. This water helps relieve gastrointestinal discomfort by reducing acidity [27].

According to Verploegen et al. [28], water evaporating through the pores of an earthen vessel keeps the remaining water inside cold. This might be the reason why the temperature of the water samples (both tap water and tank water)) kept in the clay pot vessel decreased to 24 °C at the end of the 7 days in the current study. The earthen pot’s particular property, which no other container possesses, is that it transfers coolness to the water according to the weather [27]. Compared with plastic containers, clay pots are more frequently used in the rural community to store water across all houses. This can be due to the affordability of plastic containers, the cost of making clay pots, or the fact that clay pots help in lowering the water temperature [29].

In the present study, for tap water and tank water samples in clay pots, the TDS of each water sample was found to be quite low in comparison to Egyptian law [19]. TDS in tap water kept in clay pots significantly decreased (p < 0.05), while TDS in tank water also kept in clay pots was not substantially altered (p > 0.05), which explains the significant difference between tap and tank water. The findings for tap water and tank water were compatible with the results of calabash clay pot vessels and other vessels, respectively [30]. Another research using clay pots had lower observations (64.4, 70.1, and 88.5 mg/L) [24] than this study’s results, which might be because the original TDS of our study’s samples was very high (338 and 324.33 mg/L for tap water and tank water, respectively). The elevated TDS of water samples in clay pots may be attributed to an increase in the mineral quantity, influenced by the properties of clay compared to other materials for containers, such as steel vessels or plastic bottles. The decreased TDS observed later could be due to the settling down of the minerals present in the water [25].

Electrical conductivity is an indirect indicator of dissolved inorganic particles because it measures the extent to which water can conduct an electric current. This aids in determining whether water is suitable for domestic and agricultural usage [25]. The EC values in the current study for tap water and tank water, ranged between 257–546 and 288–881 s/cm, respectively, which was greater than the finding of Neethu et al. [25], which was 117.3–154.8 s/cm. There was a significant difference in EC values between tap water and tank water samples, and there was a distinctive significant difference in the initial EC and the final EC in both tap water and tank water samples. This is consistent with the results of a study in Nigeria which showed a significant difference in EC for water stored in a clay pot (47.67 μs/cm) in comparison with the original value of EC (50.57 μs/cm) [31].

The findings of the present study showed that there was a significant difference in turbidity between tap water and tank water samples, but only tap water samples had a significant difference between the initial value and the end value, while tank water samples had no considerable differences. In this study, the reduced turbidity observed in clay pot-stored water may reduce vessel bacteria, protozoa, and helminths as well as improve taste and smell [30]. The turbidity removal in this study was higher than that observed by Obianyo et al. (2020 (6.33 NTU) where turbidity of water showed a slight but significant variation after storage in clay pots [31]. This decrease in the turbidity value of water after placing it in a clay pot container is a sign that the water quality has improved.

In the present study, the DO of each water sample stored in the clay pot was found to be high (7.46 and 7.49 mg/L for tap water and tank water samples, respectively), which accounts for the lack of statistical significance between the two types of water samples (p > 0.05). However, there was a significant difference between the two time periods (before and after storage) (p < 0.05). In another study, it was reported that the DO of each water sample held in a clay pot was high (7.25 mg/L, 6.75 mg/L, and 7.1 mg/L, respectively) which is consistent with our study’s results [24]. In addition, DO in the water samples (tap water and tank water) increased significantly (p < 0.05) in clay pots, which is consistent with the findings of research using calabash and clay pots [30]; however, there were no significant effects on DO for water held plastic and metal vessels (p > 0.05). In our study, there was a significant difference between tap and tank water samples.

In the current investigation, the chloride concentrations of tap and tank water samples were not substantially influenced by their storage in clay pots (p < 0.05), and these results are consistent with Duru et al. [30].

The recommended level of ammonia according to Egyptian drinking water guidelines is 0.5 mg/L [19], which is consistent with the findings of the present study. In this study, there was no significant difference found in ammonia levels between clay pots filled with tap water and those filled with tank water, and there was no significant difference before and after 7 days of storage in both tap water and tank water samples, which confirms that there was no significant conversion of ammonia to nitrate. Nitrate and nitrite in drinking water are thought to induce cancer in the gastrointestinal and urinary tracts, as well as at other locations, because they function as precursors of genotoxic N-nitroso compounds in endogenous nitrosation [32].

Carbonates, bicarbonates, sulfates, Ca and magnesium chloride, and chlorides are the main causes of drinking water hardness [33]. The present study indicated that the hardness and its fractions (Ca hardness and Mg hardness) of each stored water sample showed no significant differences between the initial and final values. There was a significant difference (p < 0.05) in the total hardness and its fractions (Ca hardness and Mg hardness) between the two types of water samples (tap water and tank water). The hardness of both water samples was slightly higher than the results of a study using clay pots (200, 200, and 150 ppm, respectively) [24]. Since the clay or minerals used to make the pots include hardness-containing ions, the total hardness of the water in the pot increases [34].

Chlorine is widely used as a disinfectant, particularly in underdeveloped nations such as Egypt. One of the most important steps in stopping the spread of potentially fatal waterborne infections is chlorine disinfection [35]. There are various causes for disinfectant depletion, which can have an impact on their effectiveness. Disinfectants react readily because they are strong electron acceptors and oxidizing agents. For instance, depletion of disinfectants may result from a biofilm developing in the water distribution system. In addition to photodegradation, pH, and temperature, other factors can contribute to disinfectant depletion which affects their effectiveness [36].

Consequently, in the present investigations, the TPC declined over time while the chlorine concentration had no significant difference before and after 7 days for tap water, while tank water’s chlorine concentration showed a significant difference before and after 7 days, which might be because the higher TPC in tank water compared to tap water caused the consumption of chlorine with the TPC of tank water. Chlorine reacts with both inorganic and organic substances (such as metals and humic and fulvic acids) when added to water, rendering it unsuitable for disinfection. The amount of chlorine consumed in these reactions is known as the chlorine demand of water and is calculated empirically. The remaining chlorine is known as the total chlorine residual (TCR) once the chlorine requirement is satisfied. Chlorine residuals are thought to completely prevent biofilm accumulation, which lowers the dangers connected with biofilm for water quality and public health (such as discoloration and any related microbiological mobilization). This belief is still prevalent in the water industry and the general public [37].

Zinc (Zn) concentrations above 3.0 mg/L in drinking water might give water an unpleasant metallic flavor [19, 38]. The results of this study showed a significant increase in Zn concentration from the beginning to the end, but it was within the acceptable limit [19]. Zn is less harmful to human health, and its deficiency may affect immunological function, growth, and neural development in humans [39].

Based on the results, clay pots proved their efficiency in decreasing some physicochemical parameters (EC, turbidity, ammonia, TDS, TPC, and Legionella) and increasing others (DO, chloride, and Zn). In clay manufacturing, clay is combined with water and organic components and burnt at a high temperature. It develops porosity, mechanical strength, and chemical stability or inertness [40]. Most clays remain robust even after burning at temperatures exceeding 1000 °C. To achieve temperatures above 1000 °C, a kiln must be built to contain the heat [41] which contributes to its durability. As a result, the structure has pores that are both big enough to let water flow through and small enough to keep out bacteria and other impurities. This method of making clay pots should be able to filter out all particles and bacteria bigger than the pore size [13].

The composition of the clay, firing temperature, particle size, ramming (manual or hand consolidation/forming) pressure, additives, and the reaction that takes place during the manufacturing all affect the mechanism of action of these pots, the water discharge rate, and microbe elimination efficiency [42]. Adsorbents made of clay minerals include kaolinite and bentonite. Kaolin has a low expansion coefficient, superior cation exchange capacity, and great chemical stability [43]. Because of its superior cation exchange capacity, kaolinite performs well when it comes to removing ions from aqueous solutions [44]. A clay pot can be used as a cooling system to lower the temperature whereby it simultaneously raises the relative humidity inside the inner clay pot and evaporates water off the outer surface of the clay pot [45]. This action mechanism of clay explains its ability to disinfect and remove pollutants.

Pontiac fever and Legionnaires’ disease transmission are thought to be possible in water contaminated with Legionella spp. It is crucial to regularly monitor hospital water supplies for the pathogen to prevent outbreaks of L. pneumophila, especially in hospitalized patients with impaired immune systems. There is an ongoing discussion on the relationship between the presence of L. pneumophila in water samples and the danger of infection to people’s health. An investigation in the United States has established a connection between Legionnaires’ disease outbreaks in the supplied areas and the presence of the organism in drinking water samples [46]. According to the present study’s findings, there was a significant drop in the concentration of Legionella from the beginning to the end in both water samples, which proved the efficiency of the clay pot in its removal.

The correlation between different parameters was examined. There was a strong correlation between EC, TDS, turbidity, temperature, DO, and total hardness and its fractions (Ca hardness and Mg hardness), while there was a weak correlation between TPC and Legionella.

Of the studies included in a research article, electrical conductivity (EC) was the second most frequently used indicator of water quality. Although there was a link between the TDS level and EC, 10 of the 24 (42%) investigations used EC as a dependent variable. This was demonstrated in the study by Akuffo et al. [47], where the EC value increased in correlation with the TDS value. According to standard methods for water and wastewater analysis [18], the conductivity of water is influenced by the dissolved solids present. Since the EC and TDS of water are interdependent, as TDS drops in the clay pot, EC declines as well, and vice versa [48]. The findings of the present study are consistent with the significant correlation between TDS and EC. In addition, because conductivity measures how well water can carry an electrical current, it is correlated with the ionic composition of the water. This indicator is useful because sudden or severe fluctuations at the organism level can indicate issues with the water supply. The water must be “acceptable to consumers and [there must be] no abnormal change” to meet the parametric value for turbidity (at the tap water) (1.0 NTU). Nonetheless, it must be emphasized that this value refers to how well the water looks [6]. This was consistent with the correlation between TDS and turbidity.

The water directly contacts the air in clay pots, increasing the DO of the water, which explains the negative correlation between temperature and DO [48]. According to published data, the rate of calcite dissolution increases sharply from pH 4 to 1, but it is rather flat across the center of the pH range before declining slightly once more at high pH [49], which is compatible with the research results as the pH was approximately 8, and there was no significant difference in the CaCO3 concentration. In addition, this explained the non-significant difference in the total hardness and its fractions before and after 7 days.

Finally, earthen pots can cool liquids without using energy. They biodegrade naturally into the Earth but can also be recycled and reused. Earthen pots are environmentally beneficial owing to their esthetic value. The proposed design concept offers a method for natural water filtering and purification. Doing this at home is both simple and affordable [27].

Two major limitations in this study that could be addressed in future research. First, the study focused on one type of clay pots which were purchased from a random seller. Second, there was a lack of previous research studies on this topic. Regarding the first limitation, due to some financial limitations, the team was not able to study many types of clay pots and investigate the different soil structures that those clay pots were made of or even the process of producing the clay pots. The team believes that this may have a significant impact on the way the clay pot reacts as a method of water treatment. Therefore, it is recommended that further studies explore this aspect in greater detail. Furthermore, financial limitations made the research team able to experiment for only 7 days, and this hindered them from making longer-term observations of the water quality.

As for the second limitation, the team found that there was not enough data and studies on the use of clay pots for storing drinking water; hence, this study aims at only exploring the effectiveness of using clay pots without deeply studying the causes and the consequences of using them. Most of the studies discussed the use of clay as a filter for drinking water treatment. Therefore, further research should be done to truly confirm the efficacy of using clay pots economically and sustainably and understand in depth how clay pots change the quality of drinking water.