Plumbing Question

[Vincenzo Corleone]

I live on a high floor in a 31-story high rise building and I'm in the process of going through a bathroom renovation. I've lived here for about 20 years and at some point during that time I must have gotten the impression that the water supply lines going to the shower were 3/4". I should have gotten confirmation before buying the shower system, but was given reassurances by certain people.

So I bought a shower system that will have a rain shower head on a shower arm coming from the wall, coupled with a hand held shower head that will be connected to the water supply with an elbow, also from the wall, on a slide bar. I bought a thermostatic valve that is 3/4" with separate volume control valves only to learn later that the water supply pipes are, in fact, only 1/2".

I'm seriously concerned that once everything is all connected that the water pressure will be very disappointing - to the point where I'm losing sleep over it. The valves and corresponding trims I bought can be returned but it'll be very expensive to do so. Does anyone have experience with this scenario or is experienced enough to know whether my fears are well-founded or not?

 

[sengsational]

You're almost certainly wasting your time worrying about it.

I had a 3/4 line going to a bathtub and changed it not only to a 1/2 inch, but also ran it through a valve and a heat exchanger. I timed filling up a 5 gallon bucket before and after. The number of seconds difference was less than my ability to time with the stopwatch. And of course the volume of water is much greater in the bathtub spigot than any showerhead.

 

[Out-to-Lunch]

Of course, it will depend on your available water pressure. I realize you told us that you are on a high floor, and you probably don't know the water pressure.

If both heads are 2.5 gpm, and you are intending to use both heads at the same time, a 1/2" line can handle that (marginally) if the water pressure is reasonable. By "reasonable," I mean as little as 10-20 psi.

 

[38Chevy454]

I agree, the flow rate of your showerhead is the limiting factor vs the 1/2 vs 3/4 pipe size.

 

[Aerides]

I don't know much about actual plumbing, but a rain shower showerhead is not a choice for a lot of pressure. By design, the water is dispersed via a wider head, to get a rainfall effect, not a strong pulsing shower effect.

I originally wanted one of those when we remodeled, but when that was explained to me I figured that was not the every day shower experience I wanted. I've used a couple in hotels, and they are nice, but not super practical.

 

[Vincenzo Corleone]

I greatly appreciate the responses that I've received thus far.

As much as I appreciate them, I remain skeptical. Here's why. Some of the responses speak of flow rate (gallons per minute (GPM)). But I've read that flow rate is separate and different from pressure. The author of the thing I read (the credentials of whom, admittedly, I know nothing about) made an analogy with a garden hose. The volume of water coming out of a garden hose can be high. Put your finger over the opening where the water is coming out and it increases the pressure. I remember doing this when I was a kid and it makes sense to me. Water volume and pressure - two separate things.

I hope I'm wrong about this.

 

[Vincenzo Corleone]

I don't know much about actual plumbing, but a rain shower showerhead is not a choice for a lot of pressure. By design, the water is dispersed via a wider head, to get a rainfall effect, not a strong pulsing shower effect.

I originally wanted one of those when we remodeled, but when that was explained to me I figured that was not the every day shower experience I wanted. I've used a couple in hotels, and they are nice, but not super practical.

Thanks for your response. Yes, I should have made it clear that my concern was over the hand held shower, not so much the rain shower.

 

[skyking1]

Both the pressure and volume of water in your high rise apartment are controlled by pumps and regulators. The 1/2" piping is not going to be the problem. You will have sufficient flow for whatever fixture you choose.

 

[old medic]

Thanks for your response. Yes, I should have made it clear that my concern was over the hand held shower, not so much the rain shower.

Your hand held is supplied by a 3/8 in line so doubtful you will notice a difference.

 

[Vincenzo Corleone]

Your hand held is supplied by a 3/8 in line so doubtful you will notice a difference.

So the 1/2" supply lines will feed a 3/4" valve, which, I believe will cause a decrease in the pressure (hopefully by an imperceptible amount). And as you rightly point out (and something I didn't consider), the 3/4" valve will feed into the 3/8" hose going to the shower head. My knowledge of physics is severely lacking. it seems you're suggesting that will "restore" (for lack of a better word) any pressure lost at the 3/4" valve or make any loss imperceptible.

 

[pb4uski]

I agree with others that connecting 1/2" to 3/4" is unlikely to be a problem unless you have particularly poor water pressure.

But why not just return the 3/4" fittings and buy the same thing in 1/2" if those fittings are available in 1/2"?

 

[Vincenzo Corleone]

I agree with others that connecting 1/2" to 3/4" is unlikely to be a problem unless you have particularly poor water pressure.

But why not just return the 3/4" fittings and buy the same thing in 1/2" if those fittings are available in 1/2"?

Returning them will be very expensive - high return/restocking fee. I was hoping to get confirmation that my fears were unfounded before I consider going through that expense. It sounds from everyones' responses that I needn't worry.

 

[skyking1]

the fitting size is truly irrelevant. It is the end of the line that matters and that 3/8" ID handheld hose is it.
Just for kicks, let's say it was a 1/2" hose. Do you use 100% hot water? NO
So you still have more volume available than you can use. None of this addresses the flow rate of a handheld shower head, which is much less than an open hose is.

 

[old medic]

So the 1/2" supply lines will feed a 3/4" valve, which, I believe will cause a decrease in the pressure

Your dealing with 2 different things... Pressure and volume. The pressure will be unaffected by the 3/4 inch valve body... Its not effected by a 50 gallon water heater is it?
Volume or the Gallons per minute would be more of an issue, Regardless of the valve size, you will only get what the system will supply.
If the supply is 10 gallons per minute (GPM) at 50 Pounds Per Square Inch (PSI) and your shower head is rated at 7 GPM... then you have plenty of water and pressure. If the rain head is rated at 10GPM your good, until you turn on the hand held... then the total GPM gets exceeded but the supply pressure is still the same... The flush the toilet hot shower syndrome.

 

[Vincenzo Corleone]

Sounds like I'm worried over nothing ! Thanks, everybody!

 

[skyking1]

you are welcome and enjoy your new shower.

 

[sengsational]

So the 1/2" supply lines will feed a 3/4" valve, which, I believe will cause a decrease in the pressure (hopefully by an imperceptible amount). And as you rightly point out (and something I didn't consider), the 3/4" valve will feed into the 3/8" hose going to the shower head. My knowledge of physics is severely lacking. it seems you're suggesting that will "restore" (for lack of a better word) any pressure lost at the 3/4" valve or make any loss imperceptible.

Here's something to increase your physics knowledge. Take any 3 pipes of different diameters. Hook them up to a source. The output volume will be the same, and controlled by the smallest diameter. So in your example, the 3/8 is going to be the controlling diameter, irrespective of the fact that it comes last. Imagine an extreme in order to cement the point. You have a pinhole sized pipe, a 3/4, and a 3/8 connected in a row. No matter what order you connect them, you're going to get only what the smallest allows. You might imagine if you put the pinhole last it would "spray harder", but the volume would be the same, and so out of a shower head, exactly the same, irrespective of the order.

 

[Vincenzo Corleone]

Here's something to increase your physics knowledge. Take any 3 pipes of different diameters. Hook them up to a source. The output volume will be the same, and controlled by the smallest diameter. So in your example, the 3/8 is going to be the controlling diameter, irrespective of the fact that it comes last. Imagine an extreme in order to cement the point. You have a pinhole sized pipe, a 3/4, and a 3/8 connected in a row. No matter what order you connect them, you're going to get only what the smallest allows. You might imagine if you put the pinhole last it would "spray harder", but the volume would be the same, and so out of a shower head, exactly the same, irrespective of the order.

At the risk of sounding ungrateful for your input (I'm VERY grateful), and at the risk of belaboring a point that may or may not be valid:

To be clear, I'm concerned about pressure (psi), not volume (gpm). Maybe what you're trying to tell me (and I'm just too thick to get it) is that both of them go hand-in-hand.

 

[RobbieB]

Half inch pipe will be fine.

 

[ERD50]

At the risk of sounding ungrateful for your input (I'm VERY grateful), and at the risk of belaboring a point that may or may not be valid:

To be clear, I'm concerned about pressure (psi), not volume (gpm). Maybe what you're trying to tell me (and I'm just too thick to get it) is that both of them go hand-in-hand.

Preface - this is just info, to cut to the chase, you are very likely to be fine - except you haven't really provided enough info to say that definitively.


Yes, they do go hand-in-hand. Earlier, you said: "Water volume and pressure - two separate things.".

A more meaningful/informative/relevant way to say that is: "Water volume and pressure - two separate, but interelated things."

In normal applications, one affects the other. So it isn't useful to say "I'm concerned about pressure (psi), not volume (gpm)", in this case. The volume affects the pressure.

Here's what you need to know to allay your fears:

What is the total gpm volume of the shower head (or heads if you will run more than one at a time)?

What pressure is required for the shower to work as expected at that gpm flow? The manufacturer should be able to supply this information.

Next: Can your pipe supply that volume at that pressure? Two ways to check that - you could connect a pressure gauge and a valve, and adjust the flow to that rate (measure seconds to fill a 1 gallon container). Or, if the ratings are similar to your current shower, and it works OK, then you should be OK.

If this shower isn't dumping a lot more water than your current one, I suspect you'll be fine. But w/o that info, it's really an unknown. But IME, 1/2" pipe is commonly run to individual fixtures, 3/4" is only run where it supplies taps to individual fixtures that might be run at the same time. Which is why RobbieB says "Half inch pipe will be fine. "

-ERD50

 

[MC Rider]

I say hook that stuff up.

If you have to uninstall and eat the return fees after, so be it.
Hopefully that will not happen.

 

[Jerry1]

Good luck with your build. I wish I had a better answer but you’re just going to have to hook it up and see how it goes. I’ve done this three times and only once did it work. By working, I mean that when I turned on both the shower head and the hand held at the same time did I get a reasonable experience out of both heads. I’ve never had it where only one head at a time didn’t work just fine and I don’t think 3/4 versus 1/2 will make any difference. I think the pressure coming in from your main is the deciding factor. That and the flow at each head.

 

[street]

You're almost certainly wasting your time worrying about it.

I had a 3/4 line going to a bathtub and changed it not only to a 1/2 inch, but also ran it through a valve and a heat exchanger. I timed filling up a 5 gallon bucket before and after. The number of seconds difference was less than my ability to time with the stopwatch. And of course the volume of water is much greater in the bathtub spigot than any showerhead.

You will not notice the difference just like sengsational test shows. You are good to go.

 

[Vincenzo Corleone]

Thanks, everybody.

I always learn something new on this site. Not too long ago I posted a problem I was having with my dishwasher water valve failing relatively often and learned from you fine people that my issue was water hammer. I installed a water hammer arrestor which seems to have done the trick.

I'm grateful. Sorry to those of you who may have been turned off by what may have appeared to be my challenging your responses - it really wasn't me challenging you or doubting you, but me trying to become educated on this stuff.

 

[Ronstar]

This doesn’t have much to do with op’s pressure questions, but I’ve been told that high rise buildings like his have equipment on each floor that maintains water pressure for that floor such that every floor has essentially the same water pressure.