Question about Delta Rough in valves - shower only vs shower and bath

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msimm15

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Hi I had a question regarding pressure loss on the Delta rough in valves. I know the rough in comes as a shower only with no connection on the bottom and as a shower + bath - with the connections on top and bottom.

When looking inside the Shower/Bath rough in there is a tube inside that sends the water to the tub first and then diverted back up to the shower when the tub spout is closed. Is there a significant loss in pressure in this setup ?

I had to use a shower/bath rough-in (bottom was capped) for a shower only setup because I couldnt get a "shower only" rough in at the time. The pressure isnt great, it could be because of the piping setup in the wall - (1/2" line supplying to bathrooms), but I was wondering if it had anything to do with the rough in valve.

BTW I did see a hack on line where some guy drilled through the inner tube, not that I would want to do that - just saying.

Thanks
 

msimm15

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I just read on another post that either the rough in should have been flipped so the tub end was facing up and the shower end gets capped or the shower end should have been capped and the shower should have been piped with elbows up from the bottom ?

oops - is this a big deal ? I have access to the back side of the wall if we need to rip it open and make the repair
 

LLigetfa

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When I installed the rough-in, I capped the constricted shower port and plumbed the shower to the larger tub filler port. I don't think it would have made much difference given the GPM I use but then there is nothing special with my shower head. I did however remove the flow restriction in the head.
 

msimm15

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My issue is really more when I have another shower or 2 running at the same time. The 3rd (shower only rough in) suffers.

Would I benefit by flipping the piping to run off the tub connection
 

Jadnashua

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Are all of these fed with a single 1/2" supply pipe?

FWIW, the Copper Institute's design guide calls for a hot pipe's maximum velocity at 5fps...on a 1/2" copper pipe, that equates to about 4gpm. Most shower heads are rated at 2.5g (max, some are less). SO, if three of them were running, at the worst case of 2.5gpm, that's 7.5gpm, of which maybe 5-6g would be hot...easily exceeding the maximum flow rate. IN that case, the noise goes up, the friction goes up (causing a loss of pressure), and the volume goes down because of the pressure drop and friction. So, it's not unusual to see the flow drop in your situation, and nothing you do in a single shower would help. Nothing you do other than make your supply pipe bigger from the source will help that unless your STATIC (no flow) pressure is really low...then, you could add a booster pump to bring it back up to normal values. You can't maintain pressure and flow unless the supply is sufficient...yours is undersized. A 1/2" pipe might supply two showers without a significant loss, but as you've seen, that third one is the killer. Ideally, you'd have a 3/4" or larger pipe feeding things, then only branch off to 1/2" for individual items. A 3/4" pipe can safely handle twice the volume before it starts to show the effects of excess friction. The number of elbows the water has to flow past also makes a difference in the DYNAMIC (not static) pressure...each elbow adds friction, and decreases the maximum flow through the line as does the distance it has to travel. Note, pressure will also drop at 0.43#/foot elevation it has to go up, so if one shower was in the basement, and the third was on the second floor, the pressure would be maybe in the range of 8# lower if it had to go up nearly 20' to get to the showerhead.
 

msimm15

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Yeah thats basically my problem, 2 of the showers are one on top of the other (2nd and 3rd floor), both fed from a 1/2" pipe riser. The original riser was (about) 1/2" so it was just continued up to the 3rd floor for new shower. The 3rd shower is in the basement and closer to the original 3/4" line before it changes to a 1/2" riser. It would have required ripping up a lot of walls in the house to change the riser to 3/4", and I was hoping to run low flow heads but they down seem to work well at all.

Was there such a thing as a 5/8" line. I measured the original riser - it was not copper but some other material and was about 5/8" ID - not 1/2" or 3/4".

At this point I am considering connection a booster pump to add about 15 psi on the hot line, will that not work if the riser is 1/2"
 

LLigetfa

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At this point I am considering connection a booster pump to add about 15 psi on the hot line...
I would not boost just the hot line as it would likely mess up the anti-scald balance. You need to boost the both the hot and cold.

What is the static PSI coming into the house?
 

msimm15

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I can get 45-50 psi on each shower alone, but with all them running its pretty poor. I havent checked actual pressure with them running yet.
 

LLigetfa

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Where is the pressure measurement taken and does it drop much at that location with use?
EDIT: Was typing while you were.
Take a pressure reading close to where it comes into the house.
 

msimm15

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What I meant by boosting the hot side was - boosting the cold into the indirect boiler, is it really such a problem if I boost to 65 psi ?
 

msimm15

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I put a gauge on the shower head connection (removed head and connected gauge). I only checked static pressure, didnt have a change to put the gauge on to check residual
 

LLigetfa

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What I meant by boosting the hot side was - boosting the cold into the indirect boiler, is it really such a problem if I boost to 65 psi ?
You need to boost the cold before it branches off to the boiler inlet so that both hot and cold have the same pressure. There is nothing wrong with having 65 PSI. Code allows for up to 80 PSI.
 

msimm15

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Ok I follow not the issue with the anti scald. In that case I would have to boost it when it comes into the house
 

Jadnashua

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I don't think you'll see much difference. You basically have too much resistance in the piping, and the elevation change doesn't help, either. You'll still have the same drop in pressure due to elevation change, regardless of where you start from. Pushing water faster through the piping is asking for long-term problems - increased noise, increased internal wear and tear (it can actually, literally, wear a hole in the pipe from turbulence if you pump it too fast), not counting the complexity and cost to run a pump. You really want lower resistance, and that takes larger supply pipes. You can sort of compare it to drawing electricity...draw too much power, and the wire can overheat and give you issues...the only way around that is a larger wire. Since the speed of electricity isn't an issue, you can increase the power available by changing the 'pressure' or voltage, but upping the water pressure, and the water can't really safely flow faster and that analogy starts to fall apart.

You would see some difference, but the cost may not be worth it, and the end result wouldn't likely be dramatic.
 

Jadnashua

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Was there such a thing as a 5/8" line. I measured the original riser - it was not copper but some other material and was about 5/8" ID - not 1/2" or 3/4".

Is the pipe metal or plastic? Copper typically used in a home is measured by the nominal ID, and I've not seen any 5/8"...a typical 1/2" copper pipe (and pex and CPVC, too) are 5/8" OD. 3/4" plastic pipe might end up closer to 5/8", but the OD would be closer to 7/8". Galvanized steel would have other nominal sizes. Knowing the material is key here.
 

msimm15

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The original pipe was brass I believe. I measure the I.D. with a digital micrometer and it was about 5/8"
 
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