2 Pex lines to a Urinal out of the question?

I like overkill. But I also like to be sure I am doing something "enough" for what I need.

So here is the situation.

I am plumbing in my garage bathroom and I went with the Manabloc and Pex tubing. The manifold is all 1/2" feeds. (I have the adapters to knock it down to 3/8" for the proper fixtures.)

I am installing a urinal in the bathroom. (The garage has a 1" supply line from the well.) The input on the urinal is a 3/4" NPT. Would a 1/2" supply line from the manabloc (home run of course) be enough supply for a urinal using a Sloan valve (1 GPF) or should I tee in 2 feeds to a 3/4" feed? I have the space on the manabloc to do it.

If it matters, the garage has a drinking fountain, utility sink, bathroom lav, toilet, urinal, and shower. But I am 99% sure that no 2 will be used at the same time.

Thanks in advance.

BTW: Terry, I know it is a bit late, but congrats on the Lasik. I had it done about 4 months ago and I don't regret it a bit.

Is my idea that out of control that no one has any input? Or is it just that no one is using pex from a manifold?

BTW: I got all the tubing installed except the urinal. This PEX stuff is pretty sweet.

single pipe, large size.

well i know enough in general to say that it is always wiser to upsize a single pipe than to try to achieve the same result with two smaller parallel pipes. So that is one piece of information.

Next: do you also know that "friction losses" are what reduce dynamic water flow and pressure? Do you know that water going through a single 1/2" restriction is a loss (but not critical) and so that after that "system loss" it is better to avoid all other unnecessary friction losses? For that reason, I'd probably use 1" pipe from there on over to the urinal. Assuming I had to use the 1/2" oulet from the manifold. But it's a real good idea to do it right the first time instead of jigging half-@ss solutions, and I'm not a Pex manifold experienced person. If I got called up by a friend to come over and help him and if we had NO time and had to do something immediately, and if he had all the spare parts for everything but only that manifold, I'd use two 1/2" outlets and add reducers (expanders) to 3/4" and then tie them together with a 3/4-3/4-1" tee and pull that 1" pipe over to the urinal and then reduce back down to 3/4" there. Just dreaming. But that would ensure that after the first bottleneck (AT THE MANIFOLD) there would be very little system loss thereafter. And besides, a 1" pex pipe carries only a little more water than a 3/4" copper pipe.

i'd find out whether the urinal is designed with a healthy margin (plenty of water) so that a 3/4" pex pipe wouldn't be too small. Do you know that the inside diameter of Pex is smaller than the I.D. of copper? There are tables that show how much dynamic pressure you can expect from pex of various sizes -- over so many feet. You also have to calculate in terms of the total distance.

Definitely 1/2" pex is small. Even 3/4" is small compared to the industry point of reference: copper. When a manufacturer says "3/4 inch" they mean with respect to the industry reference so they mean "equivalent in carrying capacity to a 3/4" copper pipe." Whew.

Do you know that pex fittings (and connection points in the manifold) have extremely small diameter insides? When I said above that the single restriction of one 1/2" connection point might not be critical, I was speaking very optimistically and without any first hand experience with urinals requiring 3/4" pipe. To hedge my bets, I'll reverse that position now.

What can you do to find out more from the manufacturer about what that urinal really needs in terms of dynamic pressure? Then, you must do the math without asking the manufacturer for their blessing. Math means measuring distance and multiplying it to get system losses for distance, and then adding to to losses for connection points (fittings, manifold).

david