Is 1/2 inch PEX okay for a typical urinal flush valve?

[owkaye]

Using 1/2 PEX throughout the house. New construction. Installing this urinal

Maybrook-.5-1.0-gpf-urinal-washout-action

Will 1/2 inch PEX provide enough water volume for this valve

Exposed-Manual-Top-Spud-Urinal-1-0-gpf-Flush-Valve

 

[Jadnashua]

In a short answer...no. The spec sheet calls for a minimum of 10gpm capacity, and there's no way you will get that with a 1/2" PEX line, and might not even make it with a 3/4" PEX one. 1/2" copper, using cold water, is capable of about 5gpm safely, and 3/4" about double that, so that's why they call for a 3/4" line (implying copper)...PEX has a smaller ID, so cannot flow as much, and 3/4" PEX has an internal ID of about 1/2" copper.

If you have the room, you could put in a small pressure tank in the wall and plumb the outlet with the required 3/4" outlet...that would give you the instantaneous higher volume, but may be just easier to install it per the instructions and a 3/4" supply. You might find some other valve that would work with a 1/2" supply.

 

[Sponsor]

 

[hj]

It is a 'washout" urinal so the amount of water is somewhat irrelevent.

 

[owkaye]

If you have the room, you could put in a small pressure tank in the wall and plumb the outlet with the required 3/4" outlet.

I have the room but I don't think I want to do this. I'm running one-inch PVC around the house perimeter anyways for cold water hose bibs -- separate from the PEX. I'm sure I can more easily (and cheaply) tee off this line at the urinal bath to provide the volume needed for the urinal.

Thanks.

 

[owkaye]

It is a "washout" urinal so the amount of water is somewhat irrelevant.

My understanding is that when the plumbing does not supply enough volume the flush valve won't work properly. Was I wrong about this? Are you suggesting that 1/2 inch PEX will work fine with the spec'd flush valve?

 

[Jadnashua]

The pressure is one thing, assuming the specs are correct, if it could get 10gpm and it uses 1 gallon, the valve would be open for 6 seconds. Half inch pex might deliver part of that

 

[hj]

You could also use a Central or Chicago "manual" inline flush valve that uses a dashpot to control the flush timing.