Do Toilets really use water as specified?

I was curious if most individuals or people in the trade actually measure the usage of a toilet they installed?

If so, is it by reading the water meter before and after a flush, or by placing some type of flow meter in line with the water supply?

How much variation from specifications do toilets' water usage vary given proper installation (proper Critical line and fill height)?

Is a 1.6 gallon toilet, really 1.6 gallons? And how about the 1.28 gallon and dual flushers? Do most main-line manufacturers consistently hit their water usage specs in a typical installation?

Regards,

Ira

Plumbers don't bother testing for that.

I have seen tests that show they they work very closely to the advertised specs.

Measure the inside tank dimensions, measure the before and after water level: 1.6 gals = ~370 in³.
Since low flow is the fad now you may come out with somewhat higher numbers.

Measure the inside tank dimensions, measure the before and after water level: 1.6 gals = ~370 in³.
Since low flow is the fad now you may come out with somewhat higher numbers.

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That doesn't really work.
Some water goes down the drain during a refill unless it's timed out just perfect.

Old 3.5 gallon toilets would use an extra 1.5 gallons overfilling the bowl.
2 gallons to flush with, and then 1.5 down the drain after the flush was complete.

One way, would be to set it on a stand, and flush into a tank.
Then measure that water.

When the WaterSense people from the EPA came out, we used a fish tank to compare the toilets.
One day I will put that video on youtube.

"U.S. law has mandated that new toilets sold in the United States be low-flow or low-flush, which means that they consume no more than 1.6 gallons (6 liters) per flush. "
so the tank measurement should show less than 1.6 gals so the total comes to 1.6?
1.6(2.0/3.5) = more like 0.9 gal in the tank?

My [new] toilet water volume measures ~6"x~19" and drops only ~4" during the flush = ~456 cu. in. = ~0.26 cu. ft. = ~2 gals gone as the tank level drops.

The plot thickens!

I guess reading the water meter before and after 10 or 20 flushes and then dividing by 10 or 20 will give yet another number. . .?

But what you forget, is the little tube going into the overflow.

That water bypasses the tank, and goes right into the bowl.

And the bowl does not contain water like a bucket.
It falls out of the bowl.

If you keep pouring water into the bowl, the water level never rises.

So when the fill valve overfills the bowl, it keeps using water that is never measured.

What water leaves and is replaced in the tank, as Terry said, is NOT the whole picture...you have to refill (and ideally, not overfill) the bowl after you get done dumping (some, but typically not all) the water out of the tank.

The total tank volume has little to do with the total water use on a modern toilet because, unless you substitute the wrong repair parts, or hold the handle down, it should NOT empty the tank when you flush.

Replacing either the fill valve or the flapper with an alternate supplier's model can severely affect how much water a toilet uses to flush. either by dumping more from the tank, or extra down the overflow tube to refill the bowl.

Thatguy said:

I guess reading the water meter before and after 10 or 20 flushes and then dividing by 10 or 20 will give yet another number. . .?

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My water meter measures in .02 cubic feet increments and is resolvable down to .005 cubic feet, so it is relatively easy to tell my water usage per flush. This may not be true for all places however.

7.48051948 gallons per cubic foot, or 0.13368056 cubic feet per gallon

1.6 gallons = 0.21388889 cubic feet
1.28 gallons = 0.17111111 cubic feet
0.8 gallons = 0.10694444 cubic feet

To measure the water in the tank, it would be best to use a closed jar (say a peanut butter container and measure it's displacement of water. With a known displacement, you can now measure the approximate water in the tank per inch by placing it in the bowl under the water line. The increase in height is the same as the displacement (assuming perfectly vertical sides, which is probably not the case, but within an acceptable tolerance). Also, the mechanism of the fill valve will account for some degree of differenting displacement based on height of the water, so there may be some small error there as well.

Alternatively, start with an empty tank and add known amounts of water, marking the heights at each point.

Other questions one might ask about water usage is if there is a user factor? Perhaps some people hold down the handle a bit longer, increasing some small additional usage?

Maybe it would be helpful to others if people posted their real measurements so others could benefit? Manufacturer, Model #, Manufacture Date, Water usage and perhaps notes on any changed equipment (Fill valve, flapper etc)

Regards,

Ira

Terry said:

But what you forget, is the little tube going into the overflow.

Click to expand...

So the meter will read low.

Thatguy said:

So the meter will read low.

Click to expand...

If you are measuring water flow into the house with a household water meter, it would include all water to the toilet. Meter should still be as accurate as meters are (no idea of their reliability, but I suspect they are good and probably most likely fail in a manner that indicates lower volume than used).

Regards,

Ira

Thatguy said:

So the meter will read low.

Click to expand...

No, the meter will read what the meter will read...all water that comes in should show on the meter, whether it goes down the drain, or sits in the refilled toilet.