Residential Water Supply for Commercial Flushometer?

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New Member
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Tacoma, Washington
Hello Everyone,

Looking for some advice from the collective. I'm a home DIY'er and have been building out my dream garage. I recently picked up a Toto high efficiency concealed urinal flush valve on eBay for a steal at $200. It is 0.125 GPF and the supply line connection of the unit is 3/4" NPT. The house is on a well system and pressure at the tank is 30psi at the minimum. I plan to get water from a nearby sink I installed in the same area that is supplied by 1/2" PexA (hot and cold). The sink was installed before I even thought of a urinal otherwise I would have gone bigger to provide an appropriate supply line for the flushometer.

Can I combine the two 1/2" lines (cold/hot) to a 1" pex line before transitioning to the NPT connection on the flushometer to get the volume I need for the unit to work or am I ignoring some physics here.

Alternatively, after searching this site I read a post from someone in a similar position as me that used a small bladder accumulator connected to the flushometer with 3/4" pipe and a check valve in the supply line before the tee where they are connected.

Any thoughts? Thank you in advance!


Cary Austin
Staff member
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Lubbock, Texas
I once put in a water well system for a road side park in Washington. They had a hundred of those things on both sides of the road. Makes for crazy pressure with them using so little water so quickly times 200. Lol! Made a great test for a Cycle Stop Valve which solved the problem and could supply all 200 at once or just one at a time.

But with having only one and with such a small supply line I think a little 2.2 gallon size pressure tank with a low air charge connected close to the urinal would work just fine. With a 40/60 pressure switch on your pump just put about 30 PSI in the little tank and it will be able to give you a quick shot of water when needed.
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