How Would You Install The Plumbing To Maximize Water Volume And Pressure In This Bath

Mike Finley

Here is a diagram of a bathroom layout, the shower has 2 showering areas,

1 with a head and 4 sprays
1 with a head and a rainmaker

toilet
single lav

no bathtub

3/4 copper feeding the room.

How would you plumb this keeping in mind trying to maximize water volume and pressure in the shower so that both showering areas could run at the same time with the most volume and pressure you could get from them?

Where would you run 3/4 line and where would you go to 1/2?

Thanks

Moscow

The pressure will be the same no matter what you run ( 1/2 to 1 inch copper pvc pex) As for volume I would use a manifold system were you run 1 inch or 3/4 inch then supply to the fixtures off the manfold. I have done this and I have it in my own home and it works great. I have 3 bath home, we can shower in all 3 baths and never starve the showers with water however, we will run out of hot water at the same time.
Good Luck
Justin

Teetorbilt

Do you know current pressure/flow rates?

__________________
You can't solve you're problems with the same level of thinking that created the problems.

Albert Einstein

tzzzz216

If I recall you can feed 18 fixture units on a 3/4 " line but not more than 2 fixtures on a 1/2 " line . 4 fixtures on a 1/2 " for the Hot water .

Teetorbilt

Showerheads are limited to 2.5 GPM or less @ 80 PSI by the Federal Energy Policy Act of 1992. Your max use would be the 5 head setup using 12.5 GPM. Assuming that both hot and cold water will be mixed, 1/2" should do the whole job. I'd also manifold as Moscow suggested.

How distant is the water heater? I ask this because of the 3/4" feed lines. I have a friend who I worked with at the time that he built his house, he's also a Fluid Engineer. He forgot the 'end use' principal and plumbed the whole home with 3/4" expecting a more constant pressure. It worked but took forever to get hot water to some sinks that were on the end of the line. He ended up springing for a second water heater/electrician/plumber fees for that wing of the house.

__________________
You can't solve you're problems with the same level of thinking that created the problems.

Albert Einstein

747

Yep those are sweet. I ask my plumber about those he had never heard of one.

Mike Finley

Is there a resource for information about how a manifold is a method for ensuring the maximum volume and pressure?

All we do is bathrooms and we want to offer the absolute best product possible to our customers. I've never heard of how a manifold would accomplish this, and I've never heard of anybody around here using them for that reason either, so I would absolutely love to have a technique like that available to us and our customers.

woodmagman

There is a design for the body spa set up. We have found that older homes with lower water pressure due to restricted lines are subject to lower spray pressure. On our last bath reno with body spray we had to install a inline booster pump to increase the water line pressure.
All our fixtures were home run pex to a mainifold.
The problem with the body spa is that a lot of customers assume they are getting jetted spray rather then body spa.

Teetorbilt

Make your own out of 3/4-1/2" tees.

__________________
You can't solve you're problems with the same level of thinking that created the problems.

Albert Einstein

mikesewell

Physics and calculus pay BIG dividends, I'm glad I was lucky enough to get them early in my career. Virtually eliminates call-backs, re-dos and endless hours of head scratching research and diagnostic time; and, you can CREATE, not just install. Leaves your competition in the dust.

Without it, you learn the same lesson 642 times and you think you have learned 642 new things.

And remember:
Never modify them by drilling them out very carefully with your drill press so that they work PERFECTLY (it's illegal).

Best regards,
Michael

__________________
Commercial construction

Sewell Construction

woodmagman

Ah.. the voice of experience.......... brought to you by the university of hard knocks and the college of I can do better.

Mike Finley

Okay since all your physicists with the answers are not giving up any facts, let's look at some pictures and explain to my pea brain the difference.

The first one is your manifold and the second one is just piping (Just showing the cold line for easy of discussion). What is the difference in the end result here? The real issue is only the showers right? The lav and toilet are really irrelevant, it really just comes down to suppling the maximum amount of volume and pressure to the 2 shower valves.

If you run 3/4 pipe to both valves like so, how is the end result different then the manifold version?

mikesewell

The basics of Fluid Mechanics are taught in Constuction Technology and Civil Engineering Technology courses to prepare people for solving problems that involve air and water, and many other fluids that we have to deal with in the construction industry. If you plan on doing any plumbing, it's a good idea to learn a little bit about air and water.

I hope that this helps, I'll try to keep it simple:

Where the water changes direction as it goes through the tee you get turbulent flow.

Where the water exits the manifold you get flow that is less turbulent (more like laminar flow).

With laminar flow, the friction is a function of the velocity. Double the velocity and you get double the friction.

With turbulent flow, the friction is a function of the SQUARE of the velocity. Double the velocity and you get FOUR TIMES the friction.

That's why cranking up the water pressure doesn't always mean that you're going to get a whole lot more flow.

In the calculations we normally express the friction as a reduction in head (For an explanation of velocity as related to head, google "Torricelli's theorem").

For you guys who don't enjoy calculus, there are flow tables available for pipe and fittings that show loss of head (loss of pressure), or loss of velocity, or loss of flow; they're all related.

Mike, your setup would work slightly better if the water for the shower head came straight in one end, and went straight out the other end rather than going through a change of direction. Use as few fittings as you can, ells are bad, use long sweep ells when you can, and of course tees that change the water's direction are the worst. Valve selection is very important as well, some are very restrictive and cause a lot of turbulence.

The cross sectional area of a pipe is a function of the square of it's diameter. So, if you decrease the diameter of a pipe to 1/2 of what it was, it's cross sectional area becomes 1/4 of what it was. Makes for a LOT more turbulence, a LOT more friction, and a LOT less flow. Long story short, if you want more flow, it makes more sense to get it by increasing the pipe size rather than by increasing the water pressure.

If you can cultivate a relationship with a good engineer, or a sharp plumber, he/she can help you out with a lot of this stuff.

I was a full-time plumber for 15 years. That's what really got me interested in engineering in the first place. Doing service work, you'll make LOTS of money if you can diagnose problems FAST, and get things fixed right the FIRST time. If you can't do this you will constantly be on call-backs, and you will get a BAD reputation.

Sight unseen, it's entirely possible that, in your particular case, the restrictive shower head is costing you a lot more flow than the piping is, but if you bore it out you will probably get the electric chair.

Hope this does it for you. I'm working on cut and fill calculations so I probably will be too busy to return to the forums tonight.

Teetor is by far the best on this stuff. How'd I do Teetor?

__________________
Commercial construction

Sewell Construction

gmp

I would definitely put the multi- body sprays on a looped pipe system. That will at least keep the individual heads operating at the same pressure.