Tag Archives: water saving washers

Now Saving 30,000 Liters/Day in Our Pune Housing Society

ecology, , , ,

Simple Engineering Solutions to Save Water

This year (2015-16) has been a year of severe water crisis in Pune and our housing society faced a major reduction in water supply from the Pune Municipal Corporation. This housing society consists of four buildings, each with 11 floors and 33 apartments. The water use in our society has always been excessive. The bathroom fittings installed by the builder are of great quality as far as looks are concerned. However, they assume an infinite supply of water! These bathroom fittings were the primary reason for the excessive water use. Once the water crisis hit us, we implemented a number of innovative but simple measures which are helping save about 30,000 liters of water each day. This blog-post describes some of the simple engineering solutions that helped us save water. They can potentially be implemented in every housing society with high-rise buildings and the so-called modern bathroom fittings.

Key Principle:

Water saving can be achieved by reducing the flow of water from each outlet. In our case, the water flow ranged from 7 liters/minute to more than 20 liters/minute, depending on the floor where the measurement was carried out. It was considered necessary to reduce the flow to, 3 to 5 liters/minute for every outlet, except the toilet flush. At this flow rate, usability is not affected in any way. Water flow through any outlet is directly proportional to the area of aperture (of washer) of an outlet and to the square-root of the pressure head. This implies that the water flow is proportional to the square of radius for a circular aperture and to the square-root of height of water tank above. Hence, water flow can be reduced significantly by simply using washers which have a smaller aperture. [Ref: Bernoulli’s Principle]

Implementation:

We implemented special washers for washbasin taps and showers. Since ‘water-saving’ washers were not available in the market, we made tap washers at home. For the shower, it was necessary to use Aluminum washers, which were made with the help from a local workshop. The cost of making washers for the washbasin was less than Rs. 5/- per outlet. These washers were made using a 1.5 mm thick sheet of Silicone rubber. The washers for shower were made in Aluminum by a local workshop for less than Rs. 20/- per piece. For the kitchen taps, it was possible to implement a solution similar to the washbasin. However, we chose to replace the complete aerator assembly with a flow controller available in the market. This flow-controller is well designed but costs Rs. 300/- per outlet. It wasn’t an option to use this flow-controller for every faucet and for every apartment in the entire society as the cost would be prohibitive. Secondly, these flow-controllers were not available for the shower and we desperately needed to save the water used for taking showers.

Design:

The washers for washbasin are mounted on the aerator assembly, which is removable. The washer is cut from a Silicone rubber sheet. Silicone rubber is easy to cut and can sustain high temperatures. The washer in the picture below has a central hole of 4 mm diameter. There is another (optional) hole of 1.5 mm diameter between the central hole and the edge. The second hole is useful to obtain a better aerated flow on the upper floors. The size and the number of holes can be changed, depending on the type of aerator and the desired water flow on a given floor. The central hole was punched with the help of a single-hole punch, available in stationery shops. The smaller hole was punched with a leather punching tool, available online or in some hardware shops. Even a cobbler can help punch the holes.

The washer for shower is made using Aluminum since the support provided by an aerator (as a base) is not available for the shower. Aluminum, being stronger than rubber, does not buckle due to water pressure. This washer is installed by first unscrewing the shower-head with a spanner and then installing the Aluminum washer below the original rubber washer. The diameter of the central hole depends on the floor (pressure head). On lower floors, with higher water pressure, a 2 mm or 2.5 mm hole was used. On upper floors, a 3 or 3.5 mm hole was necessary. These washers were made with the help of a local workshop that worked with sheet metals.

Calculations:

In my apartment on the 8th floor, water savings were calculated to be 320 liters/day:

  1. Kitchen sink: 125 liters/day : 25 minutes/day * 5 liters/minute
  2. Washbasin: 90 liters/day : 30 minutes/day * 3 liters/minute
  3. Shower: 105 liters/day : 30 minutes/day * 3.5 liters/minute

The amount of savings on the lower floors is expected to be higher. It was estimated that about 30,000 liters of water is being saved per day, based on actual measurement of water usage from the underground tank. This water saving also implies a saving in the energy use, both for the society and for the individual apartments.

Caveats:

  1. This implementation assumes that an easily removable aerator is part of the faucets. This is true for most modern faucets. The aerator provides space for fitting the water-saving washer. The shower-head also needs to be removable.
  2. We did not implement any solution for the toilet flush valves. While it is certainly possible to use the same principle, it was observed that the installed flush valves do not provide an easy access to implement a modification.

Note:

  1. We did not require a skilled plumber to carry out the installation. Either the apartment resident or a handy-man installed the washers.
  2. Silicone rubber sheet is available fairly easily. In Pune, I purchased it from Budhwar Peth. Workshops that work with sheet metals are generally present in most cities.
  3. It is necessary to clean the aerator and washer under running water to avoid accumulation of dirt etc. This is required anyway, whether water-saving washers are installed or not.
  4. On the lower floors, where pressure can be very high, it is necessary to use a Teflon tape (white tape used by plumbers) when installing to avoid leakage. This is available in any hardware store.
  5. For someone interested in implementing this in their society, I can be reached via comments on this blog, where you can provide your contact information. I don’t have any commercial interest in this; the idea is to save water in high-rise buildings where excessive water use takes place.
  6. Last, but not the least, this change requires cooperation by society management and a few willing residents who don’t mind experimentation in their home, before a large scale implementation.