Too much fall-off pressure in house

[jmcclimo2003]

Hi,

I have an issue with too much fall-off pressure when there is demand on the plumbing. A gauge on the yard spigot showed 50# with no demand, but that falls off to 20# if the shower is running, which explains why shower pressure is unacceptable if the washing machine is running or someone is using water in another bathroom, and this is obviously way more drop-off than the Watts PRV is supposed to experience with a few GPM running in the shower. I adjusted the PRV up to 70# which helps some, but I'd prefer to actually fix the problem. I checked the strainer on the PRV and it was quite clean. We do have a whole house water filter, so that could restrict flow some, but I tried replacing the house water filter when I got aggravated at the pressure one time and it didn't help. Unfortunately there is nowhere to connect the gauge immediately after the PRV so I can only see what is going on downstream of the house water filter.

Would you recommend replacing the PRV? I don't mind doing it since it looks like I can find an identically sized replacement and will only need to loosen a couple nuts to do it. I don't want to waste the time and money if it is unlikely to fix the problem though. Google tells me most PRV failures involve equalization with the city water pressure i.e. pressure too high. Even on this forum I only see one post about replacing the PRV for low pressure and it didn't work. We do have quite terrible hard water in the house, but looking inside the PRV strainer I didn't see substantial mineral buildup on the sidewalls, so I doubt the problem is mineral buildup in pipes throughout the house, but who knows.

 

[Geofd]

what kind of material is you main and branches
did this happen all of sudden
what is the pressure on just the hot water
what heats your hot water
what is the age of you plumbing system

 

[jmcclimo2003]

I believe it is all copper everywhere, that I can see anyway.
Nope, been going on forever, perhaps since we moved in 5 years ago.
I'll see if I can check, I believe the only access my gauge works on inside the house is the washer, but I haven't noticed a difference based on hot vs. cold water.
We have a tank hot water heater with gas heat. Its one of the ones that needs to be plugged in to function.
Plumping is probably 25 years old.

 

[Geofd]

I believe it is all copper everywhere, that I can see anyway.
Nope, been going on forever, perhaps since we moved in 5 years ago.
I'll see if I can check, I believe the only access my gauge works on inside the house is the washer, but I haven't noticed a difference based on hot vs. cold water.
We have a tank hot water heater with gas heat. Its one of the ones that needs to be plugged in to function.
Plumping is probably 25 years old.

i would get a gauge before any fixture
flush the water heater
is it a well or city????? find out what the pressure your getting from your source
if its copper are there any kinks/bends in the main

 

[FishScreener]

I would guess that you have a feed line which is restricted, either by size or corrosion. Most probably corrosion.

I’m getting ready to replace the 50-year old, 3/4-inch service to my house with a new 3/4-inch PEX feed. The old line has enough rust on the inside that I can’t slide a pencil into it. So 80-psi static, and about fifteen, with a 2-gpm faucet running

 

[breplum]

For sure you have a constriction, like FishScreener says.

 

[jmcclimo2003]

Thanks for the input. I assume this constriction is likely to be in supply line upstream of the PRV and probably outside the house. The pressure drops on the yard spigot which splits directly off from the basement, when starting a small load upstairs. This sound like thousands of dollars to fix, so I might delay until the problem gets intolerable. Right now I can get a reasonable shower as long as no one is doing laundry or flushing toilets. The pipes are copper until they leave the house, but our town is very old so perhaps the underground portion is galvanized and rusty.