Help with Large Master Shower plumbing

I'm building a house for my daughter & son-in-law and a large walk-in shower with no door was the most important feature requested by my daughter. I'm not convinced that a door-less shower will stay warm, so I designed it so a door could be easily added if needed. Also trying to talk them out of the body sprays entirely - or at least limit it to 1 bank of 3 instead of two. Ceiling height is 9'.

The house is dried in and the plumbers are scheduled to start in the next couple weeks. The master shower is on the 2nd floor and the water heater is in the attic about a 25' pipe run from the primary valve. Incoming water is expected to be set at around 70-75 psi, but the vertical run from the basement water tank to the water heater is about 33 feet.

Water heater is a Bradford White GX-1-55S6BN - 55 gal high performance atmospheric gas water heater with quick recovery. Planning a temp of 157F with a 130F output temp from the mixing valve. Body sprays can be restricted to only 1.5 - 1.6 gpm models if necessary. My design goal is to be able to run any 2 functions indefinitely or any 3 functions for 30 minutes.

I couldn't find any new construction plumbers that use Uponor (even if I gave them the tools), so it will be a crimped PEX system.

This is my current plan:





Here are my many questions - but feel free to critique ANY aspect of the design. It's early enough to change just about anything.

1) Is a single 3/4" hot water feed branch enough for master bath group (soaking tub, dual vanities, both shower valves) then Tee off a 3/4" for the large shower valve, or should I have them run a dedicated 3/4" line for the 3/4" shower valve?

2) Should I up-size the water heater output pipe to 1" PEX until after the master shower branches have been supplied?

3) Should the cold pipe from the tank in the basement to the water heater be up-sized to 1" PEX?

4) Is a 2" shower drain large enough and would you center it in the 5' x 7' portion of the shower?

5) Will a 1/2" diverter significantly restrict the flow from the 3/4" volume control to the 2 banks of body sprays?

6) Would you run 3/4" PEX for all the shower plumbing - even those running between 1/2" valves/fixtures?

7) Is 24" from wall the ideal location for a ceiling mounted rain shower head?

8) Is there a problem having the 2 banks of body sprays at different distances from their target?

Bonus Questions:
A) How far would you drop down the 10" - 12" Rain shower head from the 9' ceiling?
B) Where would you locate grab bars, and how many?
C) Do you see a problem with towels staying dry if they are hung in the 3' x 3' alcove portion of the shower?

D) Are there any questions that I should be asking, but didn't?

Thanks for any help you can offer.

 

D. YES.

you are proposing to build a wetroom, NO glass? are you attempting a curbless shower as well?

you will need to treat the whole room and floor like a wet room.


Grading, drain placement, waterpoofing are the first points id look into.


theres a lot more to the shower plan, than plumbing.

 

Yes, a wet room - no glass (with the exception of the door that will probably be added). There will be a curb at the entrance of the alcove.

I only asked about the plumbing because that is my only concern. The grading and waterproofing are being done by my tile guy who I'm very familiar with and trust.

 

you only asked about the plumbing?


enter quesrion D :

 

Maybe the thread title wasn't clear. Wanting to focus on the plumbing - or the general design & location of the plumbing fixtures.

Appreciate the comment about considering the waterproofing first - just saying that it already was considered and is handled. Now I've moved on to the plumbing.

 

good to hear youve done youre homework and hired a pro.

pretty cool giving your daughter the deluxe dream shower...

give her the 2 banks of 3 !!!

 

If I knew less about plumbing and had less experience roughing in plumbing, I might have tried to tackle it. But I know enough to know that there's not a chance I want to do this myself.

But the engineer in me still wants to make sure I know exactly what should be done because there are a wide degree of "pros" out there - and I have no personal experience with any of the new construction plumbing contractors bidding on this job. And if there's a problem down the road, my daughter will be looking at me, not the individual subs. Based on past experience, I have a lot more faith in the consensus opinion on that usually comes from this forum.

... and did my daughter put you up to the body spray comment? Her position is to throw my "gun" position back at me: "Better to have it and not need it, than to need it and not have it."

 

I will be paying attention to this thread as I am in the process of figuring out plumbing to our custom bath/shower in a home addition. It's very similar to the one you are designing for your daughter: Single thermostatic control valve, 4 volume control valves to control shower head, 4 body sprays, overhead rain-shower and handheld shower on opposite wall. Using all Moen products (ouch $$$!).

We too have debated the body sprays. Didn't even have them in the plan until we stayed at a B&B that had them. Better to do it now, then regret it later!

I'm here searching for DIY info, comments, tips, etc. before posting my own questions...eventually, I'm sure. Great resource here!

Tom

 

Since you say you're an engineer, run the numbers yourself on the gpm of the devices planned and your choice of WH. If you have everything running at once, a 3/4" pex line probably isn't big enough. Even in SC, the winter-time incoming cold water can get fairly frigid which can affect your recovery rates on the WH as well as the percentage of hot water required to be comfortable. While they might be already tepid in the summertime, having to raise the water temp a sizeable amount in the winter may restrict what can be comfortably used then, or limit the time you can use them. A 50g WH isn't all that big when you're dealing with a shower like that. Since this is going to be on the second floor, see if you can design in a waste heat recovery system for the drain....then, you have a chance of much longer shower times.

 

When I run the numbers, it seems that 3/4" PEX should be big enough - but if you're saying that in a real world application it likely isn't big enough, that's the kind of input I'm looking for. So you'd up-size to 1"?

The WH claims 200 gallon 1st hour supply which is the only reason I opted for it instead of a larger unit.

I have no experience with waste water recovery units accept for knowing about the concept. The plumber has never installed one because he claimed that they aren't worth the expense and they can dramatically reduce the water pressure in the system. Is there a particular unit you'd recommend?

 

What is the stated gpm at the maximum usage you are planning? A good design goal is to not exceed 5'/second of the water flow with the hot supply. On 3/4" copper, that amounts to 6.81gpm based on the copper tube handbook. The cold water can flow up to 8'/sec. Generally, they consider hot over 140-degrees F. Pex has a slightly smaller ID than copper, so the gpm would be slightly less. Higher speeds can lead to noise and potential pipe erosion over time.

The first hour usage is based on a draw at a particular rate. If you exceed that rate, you have no time for the burner to catch up or try to maintain...the faster the draw, the faster the tank's temperature will drop. Say you're drawing 10gpm...you'll have used up your 200gallons way before that first hour, and the burner will have only had 1/3'rd of the hour to run, not an hour, so it will have put in much less heat...IOW, at a higher flow rate, you'll not see that 200g in an hour since it will be exhausted and the burner won't be able to keep up. A waste heat recovery system can help that scenario by warming the cold water going in, minimizing the need for hot.

Not all waste heat recovery systems are created equal. It gets discussed fairly frequently, so a search will show up lots of discussions and some cost figures.

 

My goal is to be able to draw 7.5 gpm for 30 minutes or 5 gpm indefinitely - at a minimum. That's mixed gpm, not exclusively hot water. I'm figuring approx. 70% hot water vs 30% cold. But with the higher tank temp, I'm ball parking only about 75% of my hot water demand at the shower will be drawing from the tank - the other 25% is cold water introduced at the mixing valve.

Before I complicate the design further with a waste water recovery system, I want to make sure the existing design works - and that it would be inadequate without it.

 

Don't think you'll get 30-minutes at that flow rate. You might extend the comfort level a little with a thermostatic valve that can add more hot as the input cools off, but I think you're pushing it. Look at it this way...200g/60min = a max flow rate of 3.3gpm. Anytime you exceed that, your time before it cools off will decrease and you'll not get that flow. The calculation for first hour also assumes a certain inlet water temperature, and in the winter, you may not have that...IOW, it would be lower. If you have a deep well, the inlet water could be colder all year. SC should be much warmer than NH, but I can get 33-degree water coming into my place in the winter...makes it really tough to get long, high flow of hot water.

 

Nobody wants to even try to take a stab at any of the questions?

Should I add prizes?