Shower pressure question

[mbailey5]

I want to rebuild my 2nd floor master shower with a digital shower control system and multiple heads/jets. The current feed is a single 1/2" copper line. The pressure at the shower head with the valve halfway between cold and hot is 32 pounds. However, if a sink faucet anywhere in the house is turned on, the shower head pressure drops to 24 pounds. If a toilet is flushed with no faucets on, the pressure at the shower head drops to 20 pounds. The existing shower suffers from temperature changes when other faucets are in use. The house was built in 1994, the water heater was replaced in 2012, and I have a water softener installed where I the water line enters the house. How can I determine why such large pressure changes occur and whether a larger shower supply line must be run to allow the new system to be installed?

 

[Reach4]

If you have your own well, you could reduce the problem a bit by setting that to a higher pressure. It would only help, but not eliminate the problem.

Better would be to put in bigger pipes.

 

[Sponsor]

 

[Valveman]

I want to rebuild my 2nd floor master shower with a digital shower control system and multiple heads/jets. The current feed is a single 1/2" copper line. The pressure at the shower head with the valve halfway between cold and hot is 32 pounds. However, if a sink faucet anywhere in the house is turned on, the shower head pressure drops to 24 pounds. If a toilet is flushed with no faucets on, the pressure at the shower head drops to 20 pounds. The existing shower suffers from temperature changes when other faucets are in use. The house was built in 1994, the water heater was replaced in 2012, and I have a water softener installed where I the water line enters the house. How can I determine why such large pressure changes occur and whether a larger shower supply line must be run to allow the new system to be installed?

If the pump is cycling on and off while all those things are running, then larger lines and turning the pressure switch up will help. But if the pressure at the pressure tank is just low and stays low when using water like that, you will need a larger pump to supply the larger flow rates.

 

[Reach4]

Re-reading, I infer you have city water.

How is the pressure at a hose spigot when you run the shower and flush a toilet? You can get a pressure gauge with a garden hose thread pretty easily. I wonder how you are measuring pressure at the shower. It is unusual that people do that.

 

[Valveman]

I was assuming the water softener meant there was a well pump? But if you have city water, you will probably need a booster pump to get the shower pressure you want. Plus you will probably need larger than 1/2' lines to the shower.

 

[mbailey5]

I was assuming the water softener meant there was a well pump? But if you have city water, you will probably need a booster pump to get the shower pressure you want. Plus you will probably need larger than 1/2' lines to the shower.

Thanks everyone for the replies. I should have stated that my home uses Tucson city water. I should also say that, while I have experience with sweating pipes and running pvc for sprinklers, in-ground swimming pools, etc, I have little interior plumbing knowledge. I used a pressure gauge with garden hose thread and a 1/2" NPT adapter to measure the pressure at the shower head because I wanted to observe the sizes of the pressure drops at that point when other faucets or water usage devices were open. There is a pressure regulator valve at the point of entry to the house but I was told that setting the pressure higher could be dangerous to my plumbing (pvc and copper) or outdoor irrigation (pvc and 1/2" poly) and that it probably would not solve the pressure variations I see at the shower. Although I plan to rebuild the shower myself, I will get a plumber to modify or install additional water lines (I like the DIY route when I know what I'm doing but that's not the case here). I'm simply trying to determine what needs to be done and why to reduce the hours and number of visits (and of course the related costs) for the plumber. Although my neighbors all have one-story houses, friends with two-story homes in other parts of the city tell me that they do not have noticeable pressure changes in their 2nd floor shower and they also have 1/2" lines running to them. I'm guessing that there might only be a single supply line to the 2nd floor (two full baths) that is too small for the demand but I don't know for sure. If adding a pump to the existing system would eliminate the need for additional lines, I'm all for it and could let the plumber know that going in. Otherwise, I'll have one or more additional lines put into the 2nd floor.

 

[Jadnashua]

If you have a pressure reduction valve (prv) on the inlet to your house, assuming it is working properly, you should be able to readjust it (assuming the city water pressure is higher than what you're seeing). All plumbing in a home should handle up to 80psi. Generally, a PRV is only required if the pressure exceeds that amount.

FWIW, the Copper Institute's guidelines for hot water in copper pipe is a maximum of 4gpm with a 1/2" pipe, but they specify it in fps (max, 5fps) for velocity, but when you take the area of the 1/2" pipe, that equates to 4gpm. WIll it flow more...yes...should you do it....no. Higher speeds create more friction which means lower working pressure (not the same as static pressure).

An improperly sized/designed/maintained water softener can affect the flow rates through your whole home. Does it have a bypass valve? If you try that for test purposes, what are your pressures like?