Reduce water usage with a Dual Flush toilet upgrade

Toilets account for the majority (around 30%) of total indoor water usage in the US.

We flush our toilets with pristine, fresh drinking water. Most toilets waste much more water than what is needed to either flush just liquids or solids down the toilet. Only 4 out of 5 times liquids and some toilet paper need to be flushed which requires only half the amount of water of a full flush. So 4 out of 5 times a substantial amount of water usage can be  reduced.

Solution to save about 50% of water with a Dual Flush conversion kit:

A standard flush toilet can be converted into a dual flush toilet with a simple drop-in conversion kit (product details below).

A dual flush toilet has two buttons which allow selecting between a quick flush and a full flush. The quick flush will use up to 70% less water than the full flush. Since it can probably be used 4 out of 5 times, there is a huge potential for water conservation and $avings.

The conversion is a simple replacement of the flapper mechanism in the tank with a new device easily found in home improvement stores or online. The installation is really easy in most cases, requires no tools and takes only 5 to 15 minutes.

Dual Flush Installation:

Photo of Dual Flush kit (HydroRight) and HydroClean installation in tank

Dual Flush kit (HydroRight) and HydroClean installation in tank

The installation in our house worked perfect, but my fill valve would not fill the tank to the correct water level after a quick flush. Since the tank was only emptied about half way, the fill valve would not open up all the way and shut off too early. The result was an unpredictable water level for the next flush and then there was not enough water for a proper flush.

So I went out and purchased a new fill valve from the same company which eliminated that problem right away. As a very nice side effect, I am able to adjust the amount of water that goes into the bowl during the refilling of the tank. While the tank is filling up, a certain amount of water gets dispensed into the bowl to fill it up. The problem is that the water does not stop once the maximum fill level in the bowl is reached. The water continues running and drains away until the tank is full. This drain water is pure waste, because that water is not even used for flushing. Our old fill valve wasted about 54 fl.oz. (0.42 gallons) down the drain with each refill. The new valve has a mini valve which allows to control the amount of water going into the bowl.
Another nice feature of the valve is that it cleans the tank while refilling. This is done by directing the water through nozzles into bottom areas of the tank to avoid settlement buildup. That should help to keep the tank, the valve and the flapper mechanism clean and extend its lifespan.

The installation of both products is well documented and fairly easy.


I spent probably another 30-45 minutes optimizing the amount of water used for each flush. The following settings can be tweaked for optimal results:

  • The fill level in the tank. This level and the setting for the full flush determines the amount of water used for a full flush  It should probably be set first.
  • The amount of water in the bowl by adjusting the water going into the overflow. I adjusted it to be a little below the overflow level for the quick flush.
  • The amount of water used in a quick flush. Has to be set in combination with the level in the bowl to have the toilet bowl drain properly.
  • The amount of water used in the big flush. I set mine to minimum, since the quick flush is already sufficient in most cases.

Water reduction results:

With our 1.6 gallon toilet, the fill level in the tank got reduced by about a ½ gallon.

54 fl. oz. of water is saved for each tank refill after a quick flush by adjusting the mini valve on the fill valve. I optimized it for the quick flush (because it is used 4 out of 5 times) so there is still some overflow during the full flush fill cycle. However, it is much less wasted water than before.

The data I collected  indicates an expected savings of about 58% of water for the quick flushes and about 27% for the full flush. That accumulates to about 2332 gallons per year per household member.

Here are the economics:



Dollar Savings

Payback period [months]

1st Year ROI

Dual Flush+HydroClean (3 person HH)



less than 4


(Assumptions: household of 3, 4 quick flushed per day, 1 full flush per day, $0.0135 per gallon cost, data per toilet)

Converting one toilet in a 3 person household would have a payback time of less than 4 months assuming our water rates. The return on investment is 314% in the first year only. After that the savings will be “free”.

Even without the monetary savings, it just makes me feel good to save 2332 gallons per household member per year. That is a lot of water that does not have to be treated to have drinking water quality, transported to and from our house and then treated at a waste water treatment plant again.

Product Details:

The dual flush converter  HydroRight by MJSI, Inc.
Click this image to get to the Amazon product page.
The fill valve is called HydroClean


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