Having a problem with large variations in water pressure

[txcentral]

Hi All. Thanks in advance for any suggestions that you can make.

Here's the story with as much details as I can think of to add. I'm hoping for any ideas on what to do/try next as I am stumped and the plumbing company that has looked at this is as well.

Central texas area. City water supply. We just got out of the worst low temperature storm in probably 30 years.
I did not have any busted pipes luckily. Most around here were not that lucky.
Anyway, a few weeks back I noticed that the water pressure inside the house seemed a bit down. Not unusable, but still low. I had gone out to turn on the lawn irrigation system and check out all the heads and such and when I turned the first zone on I knew immediately that I was having a big problem. Heads took awhile to pop up and had maybe 1/2 the spray distance. So, go to check the pressure at a hose bib. 42psi. Normally I run the pressure at 75-78psi. I need right around that just to get the farthest sprinkler zones to run good.

Ok, well, try to adjust the PRV right? any adjustment on the screw up or down did nothing to raise or lower the pressure at all. So at this point I'm pretty sure I have a problem with the PRV and need to replace it. I've had to have it replaced before that fixed a different problem (105psi with little flow) so figured that was probably it.

Had the PRV replaced and no change at this point.
So now I'm trying to figure out what else could possibly be the problem.
Calling the water company is of no use. If I'm getting 40psi their job is done.
So I started by checking the water pressure every hour or less on the weekend and found that
it does go back up to 75-80 and holds for random amounts of time. Sometimes half a day,
sometimes just an hour then goes back to 42. although I did see it go to about 55 a couple times.
When the pressure is at 75-80, I can adjust the PRV like I normally should be able to.
Anytime it is lower, it will not adjust, up or down.

I thought maybe I could chart the time of day that the pressure is up/down but it turns out
that it is random. With random durations of up/down in pressure.

Just because it is free to do, I thought maybe it could be a pocket of air somewhere moving around
creating a choke point so I turned on all the faucets/bibbs/showers/etc for awhile to see if that would
give me any clues or possible fix the problem. No dice no change.

I started leaning on it being something with the city supply until two days ago I got home from
work and checked the pressure and it was up to 78, so I figured for now to take advantage of that
and run one of the further out sprinkler zones that won't run properly with the lower pressure.
I ran it for maybe 40 minutes no problem. Then had to pause it to go get something from that section
of the yard. Had it off for maybe 2-3 minutes and turned it back on. sprinklers wouldn't pop up.
Went to check the pressure. Back to 42. I'm thinking this piece of information most likely resolves the
water company from being the problem.

Could the backflow preventer have anything to do with this? I have one of the Zurn double check valves.

The problem is noticed not just in the sprinkler system, but in all faucets/showers/baths. It is definitely
system wide. Our water tower for the neighborhood is maybe a block and a half away. Talking with some of the neighbors, they are not seeing any problems right now. I do have a water softener. It is functioning normally.

I can answer any questions anyone may have or find an answer if I don't have it.

 

[Reach4]

Just because it is free to do, I thought maybe it could be a pocket of air somewhere moving around
creating a choke point so I turned on all the faucets/bibbs/showers/etc for awhile to see if that would
give me any clues or possible fix the problem.

The problem is not air.

The problem is noticed not just in the sprinkler system, but in all faucets/showers/baths. It is definitely
system wide. Our water tower for the neighborhood is maybe a block and a half away.

I am a bit surprised that you need PRVs if you have water towers. I guess you are in a valley.
1. What is the pressure before the PRV?
2. Is the lawn water drawn off before the PRV or after?
3. Have you cleaned the screen on your PRV?

 

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[txcentral]

The problem is not air.

I am a bit surprised that you need PRVs if you have water towers. I guess you are in a valley.
1. What is the pressure before the PRV?
2. Is the lawn water drawn off before the PRV or after?
3. Have you cleaned the screen on your PRV?

We're in hill country, but every house here has a pressure regulator.
everything is after the regulator. It is in the ground, about 6 inches of pipe separates it from the city
water meter. No present way to check pressure between the meter and regulator.
It was replaced first thing when this problem came about, so the one I am working with is brand new.

 

[Jadnashua]

It’s more likely that your incoming water pressure is no longer holding steady like it did before the storm. There could still be numerous leaks across the system that is impacting their ability to keep the pressure up, or, some of their pipes and or pumps have been damaged, and not be able to keep system pressure up.

So, as they said, as long as they’re providing you with at least 40psi, they’ve done their job. The fact that you designed your sprinkler system on 75psi, sorry. If this ends up a long-term problem, you could add your own pump to raise the system pressure, and no, the utility doesn’t owe you anything towards that.

To see what I’m talking about, This Olde House did a session on adding a pump a number of years ago, but is (or was) available to watch on their website.

 

[txcentral]

It’s more likely that your incoming water pressure is no longer holding steady like it did before the storm. There could still be numerous leaks across the system that is impacting their ability to keep the pressure up, or, some of their pipes and or pumps have been damaged, and not be able to keep system pressure up.

So, as they said, as long as they’re providing you with at least 40psi, they’ve done their job. The fact that you designed your sprinkler system on 75psi, sorry. If this ends up a long-term problem, you could add your own pump to raise the system pressure, and no, the utility doesn’t owe you anything towards that.

To see what I’m talking about, This Olde House did a session on adding a pump a number of years ago, but is (or was) available to watch on their website.

Who knows if they are being completely honest, but according to the local water, they are back up to 100% since that storm. Took a few weeks of course. it's not so much that the sprinkler system was designed for such a high psi, as it will work ok with 65psi, but it's a large system with distance and elevation so while I may have say, 65 psi at a hose bibb, the furthest sprinkler zone will have quite a lot less.

Yes, I have looked and read a bit about a booster pump as a worst case scenario fix. I'm fine with doing that if it has to be done.
What gets me is the whole unable to make any adjustment to the PRV when pressure is down at 42. I should still be able to cause
some sort of effect during those low pressure times? That's kinda what has got me thinking maybe something with the backflow preventer.
I know that any adjustment I make to the PRV during these low pressure spells will be seen after normal pressure returns.

 

[Reach4]

What gets me is the whole unable to make any adjustment to the PRV when pressure is down at 42. I should still be able to cause
some sort of effect during those low pressure times?

Are you saying that you cannot adjust the PRV down to 30 during those times?

That's kinda what has got me thinking maybe something with the backflow preventer.
I know that any adjustment I make to the PRV during these low pressure spells will be seen after normal pressure returns.

To eliminate your backflow preventer suspicions, measure the pressure in the house. You can attach a gauge at a laundry tap or the drain on the WH.

 

[txcentral]

Are you saying that you cannot adjust the PRV down to 30 during those times?

To eliminate your backflow preventer suspicions, measure the pressure in the house. You can attach a gauge at a laundry tap or the drain on the WH.

Yes. I am saying that no amount of turning the screw in or out, in the PRV does anything to the measured pressure at any hose bibb (I have 5) during these low pressure times. During the times when the pressure is "normal" adjusting the PRV works exactly as it should.
That had me convinced the PRV had to be the problem and replaced it first thing.

I have not measured pressure inside the house via a gauge. I will do that this evening when I am home just to verify.
I can say for sure that when the pressure is low, it is not only a sprinkler problem but also a problem inside the house.
it is a night and day difference in how fast the sink can fill up a glass of water, not to mention the women in the house
complaining about having a hard time rinsing the conditioner out of their hair in the shower.

See, I thought that the backflow preventer was only on the sprinkler line, but I may be mistaken on that. I've got a call in to verify.
In thinking about this, I seem to remember that there was some county/city code about having the backflow on the main, as I have an Aeration sewer setup. and most of the county sits on an aquifer. I am not sure on this, so I've called the installer who did the backflow and sprinkler expansion for me a couple of summers ago. Guy is all about following code exactly.

Considering my neighbor who's water meter and PRV sit about 2 feet away from mine has good pressure at 70psi, it has to be something in my system. of course it is possible it is something with the city's water meter for my property. I don't want to call them in on it until I've exhausted every other possibility as they really don't want to fix anything even when it is their fault.

 

[Reach4]

During the times when the pressure is "normal" adjusting the PRV works exactly as it should.
That had me convinced the PRV had to be the problem and replaced it first thing.

Remember to dribble water when adjusting a PRV lower.

See, I thought that the backflow preventer was only on the sprinkler line, but I may be mistaken on that.

I expect you were not mistaken.

Considering my neighbor who's water meter and PRV sit about 2 feet away from mine has good pressure at 70psi, it has to be something in my system. of course it is possible it is something with the city's water meter for my property. I don't want to call them in on it until I've exhausted every other possibility as they really don't want to fix anything even when it is their fault.

Is the neighbor maybe at work during these episodes?

But yes, the problem could well be at the meter or the pipe from the main.

 

[txcentral]

Remember to dribble water when adjusting a PRV lower.


I expect you were not mistaken.

Is the neighbor maybe at work during these episodes?

But yes, the problem could well be at the meter or the pipe from the main.

Yeah, just to get the most accurate reading as possible I also open a couple valves and re-check my gauge before making any further adjustments.

 

[txcentral]

Finally got a chance to check pressure inside the house. It was what I expected, it is just a couple psi less than what I measure at a hose bibb. There is a water softener before any of the inside plumbing, so that pressure difference was expected. Still have completely random times and durations of low psi and normal psi.