Custom Shower Plumbing Rough-In Advice Needed

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Matt Duncan

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Sorry... I'm not sure if I should post this here or in the Plumbing section, but here we go...

I'm remodeling my tiled shower and will have four body jets, a handheld and a ceiling mount shower head. I need some advice. Here is what I have.

Shower Head:
is a 20" stainless steel square rain shower...

Body Jets: four Danze D460258BN Parma 2-Function Wall Mount Body Spray Jets (1/2" IPS connections) ... not sure what the IPS connection is.

Handheld Shower: Danze D464401BN Showerstick Personal Shower Kit

Thermostatic Valve:
Grohe 19878EN0 Brushed Nickel Europlus Shower Trim with Integrated Volume Control and 2-Way Diverter & Grohe 35026000 Groflex Universal Rough-In Box

Let's make this clear... I'm not a plumber and will hire a professional to do the install, but I want to make sure I have what I need to do this project correct.

First question... Can the Grohe thermostatic valve work for what I need? I want to be able to have all three outlets on at the same time if I want. Maybe it will work if I add three volume control valves?

Second question... I've noticed that some shower component are 1/2" and some are 3/4". Right now I have 1/2" PVC or CPVC from the old shower. I'm not really sure how well the pressure was since I'm remodeling a house I recently purchased and never actually turned on the water in the shower. I'm guessing it will need to be converted to copper or possibly PEX? Of course I will leave this up to whatever plumber I find to do. I know there will need to be some type of pressure loop configured.

Third question... Since I have so many outlets, do all the components need to be 3/4" or can they be different, 1/2" on some? Do I need all 3/4" plumbing? Does this need to run from the mains or where?

I'm trying to getting my ducks in a row and know what to expect when I get this bid out and know what aspect of work should be done. I appreciate any input!
 

Jadnashua

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First, you will want 3/4" copper lines all the way back to the main supply to be able to run all of those things at the same time. You could use pex, but I'd go to 1" pex. Read the specs on all of the outlets to find out their gpm flow rate...add them up, then compare that to the valve you want to use. Your valve will need to be able to supply at least that amount. Think about a hose with no nozzle on it. The water just sort of flows out. Now, start to restrict that outlet - the spray has more velocity and goes further. Your showerheads will do the same thing if the valve and its supply cannot supply more water than they need.

Second, having all of those outlets on at the same time will deplete a water heater very quickly...you'll want a significantly sized one unless you only want a few minutes. You can usually only get about 75-80% of the tank's capacity before things start to cool off.

The Copper Institute has a design manual that discusses pipe sizes, the impact of fittings and distance, and flow rates. A 1/2" line just will not satisfy you, and a 3/4" one may still be marginal. You can download it and get an education. Exceeding the design specs means higher velocity, which creates more friction, which can erode the pipe, make noises, and really mess up things. Most people abuse those design guidelines.
 
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