Very strange issue with my house water pressure - Low pressure issue

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MSgtTom

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Jun 4, 2019
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Location
Alabama
Strange issue with my house water pressure.
First - there is no PRV, and no whole-house filter or softener. Copper pipes throughout the house and 3/4 inch feeds.

Started a few months ago. The pressure is fine coming into house. If I disconnect main supply from the cold supply plumbing at the hot water heater the pressure is great. It drops (at the entrance of the main supply and rest of the house) if I connect it to the rest of the house.

I disconnected the cold and hot and drained the system, replaced some joints and 90 degree elbows, and the pressure was great for about 10 days. Now it's low again. I have checked every inch of the plumbing in the house and there is no leaks or signs of leaks.

The pressure is good for around 24 hours each time I disconnect the supply and drain the pipes.

The house has two showers, two toilets, a, hot water heater, a kitchen refrigerator, a washing machine, and a dish washer.

I need some ideas
 
I want to make sure I'm following you entirely.
Sounds like you may not be using a pressure gauge. Are you?

You say you have "great" pressure at the cold water feed to the water heater. What is this based on? Visual?

You say, "it drops at the entrance of the main supply...", if you connect to the rest of the house. What exactly do you mean when you say "connect to the rest of the house"?

I can't make a lot of sense out of the rest of the symptoms.

Sounds like you should start by checking the pressure, with a gauge, at or near the water main coming into the house. Use a water pressure gauge that has what is called a maximum indicator. A second needle(Red) that stays at the highest reading it has seen, until you reset it. That would of course show you if there are any major fluctuations over a period of time. Not unusual, for example, for the pressure to go up over night when the demand is lowest.

I'm assuming you are on city water and not a well.
 
@Diehard - yes sorry. I have used a pressure gauge. Municipal supply - I've already had them out to test the meter. With no other valves open it sits fine around 65psi. If you open another valve anywhere else in the house it'll drop down to below 20psi.

At the main entrance into the house it's pushing around 70PSI. The symptoms match a blockage - but I've replaced the pipes from the entrance to first half of the house. Same issues. Disconnect the water and drain the cold side pipe and reconnect - pressure it great for around 24 hours and then drops again.

No leaks. If I didn't know better I would say that there is a vacuum or suction on the line somewhere causing negative pressure. It's driving me crazy.
 
If the gauge is at the meter and it sits at 65 psi, and then when you flow the water anywhere in the house and that same meter drops to 20 psi, the restriction is upstream of the gauge. For example a partially closed valve or some type of blockage.

Oh wait...you say at the main entrance it's pushing 70 psi. What happens to that reading when flowing?

Where's the 20 psi reading happening? At the entrance to the water heater? If so the restriction is upstream of the gauge location. i.e.-between there and the main entrance.

The fact that the "pressure it great for around 24 hours" after disconnecting and draining water line, doesn't make much sense, unless it's allowing the blockage/restriction to open when drained and takes that period of time to restrict it again.

What type of valves or what do you have between the main entrance and the point of the low pressure test?
Valve, fittings, or anything else? Do you have a tee take off in that stretch of piping and if so, may I assume the uses on that tee branch are also suffering the same pressure losses? If so then the restriction is between the tee and the main entrance. In other words I'm trying to narrow down the area of the restriction.
 
Last edited:
When you say, "I've already had them out to test the meter. With no other valves open it sits fine around 65psi. If you open another valve anywhere else in the house it'll drop down to below 20psi.", it sounds like that pressure test was at the meter.
How did they test the meter? I hope you don't say just static pressure.
 
E- 8
my respects

sounds like you have an obstruction that is moving in your pipe
I suggest that you back blow the system

disconnect and remove the water meter
shut of every valve in your house. all the valves under all the sinks and terlets

at your water heater. drain it completely
disconnect the HOT waterpipe from the water heater
install a 100 lb test on the water heater NOT THE PIPE

fun part...pump that water heat full of air, 60 psi
then reach over and open the cold water valve on top of the water heater
what ever is in that pipe is going to get gone out to the water meter pit

gage.png
 
frodo said:
E- 8
my respects

sounds like you have an obstruction that is moving in your pipe
I suggest that you back blow the system

disconnect and remove the water meter
shut of every valve in your house. all the valves under all the sinks and terlets

at your water heater. drain it completely
disconnect the HOT waterpipe from the water heater
install a 100 lb test on the water heater NOT THE PIPE

fun part...pump that water heat full of air, 60 psi
then reach over and open the cold water valve on top of the water heater
what ever is in that pipe is going to get gone out to the water meter pit

View attachment 21022
Click to expand...
Thank you - now retired E-8.
I appreciate the assistance and advice. I will attempt the blow back.
The puzzling thing on it is the pressure is perfect after disconnecting the inside pipes.
But I agree with all your suggestions. Thank you.
 
Diehard said:
When you say, "I've already had them out to test the meter. With no other valves open it sits fine around 65psi. If you open another valve anywhere else in the house it'll drop down to below 20psi.", it sounds like that pressure test was at the meter.
How did they test the meter? I hope you don't say just static pressure.
Click to expand...

@Diehard - the truth is I wasn't there when the water company came out. They "claimed" they did both static and dynamic test.
The pressure drop is both upstream and downstream when it occurs.
I had the same conclusion as you - so that's why I started at the main entrance and replaced the piping, ball valve, and T offs past the first two (bathroom and kitchen). After that the pressure was good again - but only for about one day. That is how I originally discovered that draining the pipes temporarily eliminates the issue. I thought I had it repair - until the next day and it was back.
If I go back to the basement and disconnect the main from everything but the hot water heater line - all is well. Connect it back to the remainder of the house and the pressure drops at ALL locations. Upstream and downstream.

I will try the blow back method next - but even though the symptoms indicate a restriction in the service line the pressure static and dynamic at the point of entry don't show that. The low pressure only appears if I connect to the remainder of the house. It's crazy. But it could be something moving around I supposed. I'll blow it out and see what happens.
 
frodo said:
post back with your findings,
Click to expand...

Well - sorry it took me several days to get things figured out and solved. First things first - I tried the blow back. Disconnected at the meter box and put a big mesh net to catch the culprit coming out. Got up to 70PSI charge on the tank, but when I opened the valve guess what? No air would escape back out the service line. None. Not a single drop in the PSI.

So, today I got on the shovel and started digging. I was actually looking for the 90° going back toward the meter.

Instead...... I find that "someone" had buried a brass ball valve about 4 foot deep in the dirt. The ball valve was totally unprotected and from the looks of it the mud had it partially closed.

Anyway. I replace it into the house, correctly this time. I attached a pic of the valve I dug up and cut out.

I thank you gentlemen for you assistance and support.
 

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Diehard said:
I'll bet you felt good after the fix and getting that pressure back in the house.
Click to expand...
I had to hold on to something in the shower to keep from being knocked over. Haha.

But I would like to have a conversation with the plumber that buried that thing
 
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