What size manifold do I need to supply water to five 1.6(gpm) Water closet, Tank, One Piece; one Urinal, Valve 15(gpm), one Lavatory 4(gpm) and one Drinking Fountain Flow Rate 0.75(gpm)?

3/4" pipe should be all that's needed, then use 1/2" to each fixture. Keep in mind that all fixtures will not likely be in use at the same time. I think you are missing a decimal point on that urinal flush rate.

I would come off a 1" main with 3/4" manifolds feeding not over 3 fixtures off a 1/2" branch. Good luck, Tom

Hi all:

Just to make this clear: A urinal in itself requires a 3/4" feed. I am sure that Bob simply forgot this... ;)

As Tom stated, a 1" pipe manifold should do the job here... :) (3/4" to the urinal, 1/2" to each toilet, 1/2" cold (and 1/2" hot) to the lavatory and 1/2" to the drinking fountain).

MARK

Is this commercial job ?

Commercial or not Milo... still requires 1" minimum cold water pipe.. ;)

Let me know what you are thinking here...

MARK

I disagree with you Mark, If this is a commercial project than each plumbing fixture requires 3/4" , type L, supply. Urinals / flush valves may be 1", therefore they would require 1" supplies. Therefore, depending on developed length of the supply pipe for the fixtures given - the supply should be more like 1 1/2".

If the toilets are flushometer type toilets then I absolutely agree with you Milo... but most commercial applications in my area are now using typical floor-mount toilets so only need a 1/2" line to each... ;)

I see where you were going...for sure!

Mardin... we need more info. Here... commercial or residential? Let us know?

Milo, do they allow floor-mounted toilets for commercial application in your area..? And I have never seen a 1" urinal flushometer..???

Milo...

Mardin did say "five 1.6(gpm) Water closet, Tank, One Piece"... why I stated the size as confidently as I did... ;)

Mark, Yes, they allow floor mounted commercial toilets with tank. However, they are not too popular bcs they are constantly broken (people flush with their foot )
Yes, 1" flush valve is common (Zurn, Sloan) - at least here...