Toilet Efficiency Case Study – Part 2 – How to Measure Flush Volume and Leak Test

As promised in our previous post on toilet efficiency, we’ve inventoried the six toilets at our home and three investment properties.  Now, we’ll show you how to leak test your toilet and determine its flush volume in gallons per flush, and we’ll summarize the data for our toilets. 

Determining Flush Volume

If you live in a home that was built before The Energy Policy Act of 1992 (United States) took effect in 1994, and have not replaced your toilet, it probably has a wasteful flush volume ranging anywhere from 3.5 to 7.0 gallons per flush (gpf). 

If you don’t know the flush volume of your toilet, and you don’t see “1.6 GPF” printed right behind the seat on the bowl (along with the equivalent “6.0 LPF” for litres per flush), there is an easy way to determine it. 

You’ll need a gallon jug or bucket.  With that in hand, just follow the five easy steps at this link from the Marin Municipal Water District to determine your toilet’s gallons per flush (gpf).  Or, follow our step by step video below.

Checking for Leaks

Leak testing is as easy as coloring the water in your toilet’s tank with something safe like food coloring, waiting for a half hour, and then checking to make sure that none of the coloring has shown up in the toilet bowl.  See Toiletology 101 for more details on testing, significance of leaks, and how to fix them if you find them.  

Data for Our Toilets

• Phoenix Street Property – two 1.6 gpf toilets manufactured by VitrA, neither leak.
• Maple Street Property – two 1.6 gpf toilets, one manufactured by Fremont and one by VitrA, neither leak.
• Sunset Avenue Property – one very old toilet, brand obscure, measured flow = 3.5 gpf, does not leak.
• Buckeye Street Property (our residence) – one Crane toilet, 3.5 gpf, does not leak.

So now we’ve got the data we need to build a tool that will allow us to determine our current toilet water consumption, estimate water conservation associated with various modification/replacement scenarios, and calculate payback times. 

In Part 3, we’ll present and discuss this tool, and make it available for you to use for your own assessment.

Until then, it is worth reading and thinking about this piece on Peak Water from Twilight Earth.  It may increase your sense of urgency (pun intended) to tackle toilet efficiency and other water conservation measures, regardless of what we learn about projected payback times in Part 3.

Thanks gromgull for the cool toilet image.