Hot water recirculation pump orientation

[wwhitney]

If you have no flow in the water pipes, the pressure everywhere at the same elevation will be the same. And the pressure in the system will go down by 1 psi per 2.31 ft of elevation increase.

Cheers, Wayne

 

[Jadnashua]

MOst PRVs will have a limit on the amount they can reduce the outlet pressure. In a worst case scenario, you might need two in-line to step the pressure down. So, you need to look at the specs on the unit you want to install.

Having it outside won't be a functional issue unless it could get cold enough to freeze. Where I live, the meter and prv, are installed inside to prevent that from happening and the water line comes in below grade. It may not be an issue where you live.

 

[Sponsor]

 

[Niccolo]

MOst PRVs will have a limit on the amount they can reduce the outlet pressure. In a worst case scenario, you might need two in-line to step the pressure down. So, you need to look at the specs on the unit you want to install.

Having it outside won't be a functional issue unless it could get cold enough to freeze. Where I live, the meter and prv, are installed inside to prevent that from happening and the water line comes in below grade. It may not be an issue where you live.

Good point, it makes sense to try to get more accurate pressure readings and match the valve specs to what I'm seeing.

It basically doesn't freeze here, on rare occasions there will be an overnight frost. My water supply runs underground to my house, where the pipe emerges outside and uninsulated for a number of feet before entering the house. It might look prettier to put the valve into a box of some kind, though.

One thought: is there any upside, or downside, to installing an expansion tank now and researching the pressure reducing valve a bit more (including being in touch with my utility and my HOA)? We know my water heater isn't the source of the excess overnight pressure, but would the expansion tank help with the externally-sourced excess overnight pressure? Or conversely, would that excess external pressure damage the expansion tank (e.g. stretch the rubber) such that I wouldn't want to install an ET until I had installed a PRV?

On pressure reducing valves, lots of options around $100 at Home Depot. Obviously the local plumbing supply house will have other (or the same) options, not sure how the pricing would compare. I'm seeing max PSI either 300 or 400, so that doesn't seem to be an issue. Not sure how to think about the different options.

EDIT: I've told the plumber to put the PRV and ET on hold, I don't want to rush into a really expensive project without making sure it's going to be done right. If there's value to doing the ET now, that's a lot cheaper and I'll need it anyway, but it's not clear to me whether an ET would help with the external pressure I'm experiencing or whether that might actually damage it.

 

[Jadnashua]

IMHO, you really don't want to install an ET before you put in the PRV. You could damage it with an excessive inlet pressure, and, you certainly would be stretching the bladder lots more than it was designed for. The things are designed (with some margin) for code compliant pressures, which say NGT 80-psi.

If that pressure was a spike, maybe. IF it had any duration, no, it won't act to limit the pressure in the home. It only really works as designed in a closed system with the outlet pressure in the design range. IT's designed to protect your water system from thermal expansion, and that's a gradual increase in volume, not a generic increase in pressure.

 

[Niccolo]

IMHO, you really don't want to install an ET before you put in the PRV. You could damage it with an excessive inlet pressure, and, you certainly would be stretching the bladder lots more than it was designed for. The things are designed (with some margin) for code compliant pressures, which say NGT 80-psi.

If that pressure was a spike, maybe. IF it had any duration, no, it won't act to limit the pressure in the home. It only really works as designed in a closed system with the outlet pressure in the design range. IT's designed to protect your water system from thermal expansion, and that's a gradual increase in volume, not a generic increase in pressure.

That's what I figured.

I need to get a better sense of what sort of pressure reducing valve setup I want.

 

[Niccolo]

My overnight PSI readings so far: 140, 180, 140, 160. It's striking that they're such round numbers, kinda makes me think the utility is hitting a target pressure to pump up water tanks overnight, e.g. the system hits 140, if that doesn't fill the tank it goes to 160, if that doesn't work 180. No idea whether that's plausible, though.

I reached out to the utility, and they offered a pressure test. Not sure whether they take responsibility for the pressure at which they're delivering water? Would be great news if they installed a PRV for me, the labor costs of having a plumber do it are pretty significant.

 

[Reach4]

My overnight PSI readings so far: 140, 180, 140, 160. It's striking that they're such round numbers, kinda makes me think the utility is hitting a target pressure to pump up water tanks overnight, e.g. the system hits 140, if that doesn't fill the tank it goes to 160, if that doesn't work 180. No idea whether that's plausible, though.

Can you take a time laps movie of your pressure gauge?

You can also relocate your pressure gauge with a garden hose. Maybe put the gauge outside of a window, and have your phone camera inside recording.

If the pressure slowly rises, that would seem like thermal expansion. If the tattletale hand jumps up, but the regular hand is not way up, that would seem to be some kind of vibration or pulse affecting that tattletale hand.

 

[Niccolo]

Can you take a time laps movie of your pressure gauge?

You can also relocate your pressure gauge with a garden hose. Maybe put the gauge outside of a window, and have your phone camera inside recording.

If the pressure slowly rises, that would seem like thermal expansion. If the tattletale hand jumps up, but the regular hand is not way up, that would seem to be some kind of vibration or pulse affecting that tattletale hand.

Don't have a camera (other than a motion-activated video doorbell, don't think I could make that work). Would a cellphone record an all-night video? Actually, I suppose laptop is another option. I wonder how big that video file would get. I have a PC. I have Zoom from work, I think that would record into the cloud (is a one-person Zoom feasible?). Open to suggestions!

We've already done an experiment where I've let hot water drip overnight and it had no effect, i.e. same high numbers, so possibly we've ruled out thermal expansion from my own water heater.

The tattletale hand might overshoot slightly, but I feel pretty confident this isn't just about vibration. And the round numbers are striking too. And during the day, when the pressure oscillates between 53-58 PSI, the tattletale is tracking that well.

 

[Reach4]

Would a cellphone record an all-night video?

What cellphone do you have?

 

[Phog]

Why don't you just turn off your water heater overnight as a test? Then there is no chance of thermal expansion & any pressure you see has to come from the utility.

 

[Niccolo]

Why don't you just turn off your water heater overnight as a test? Then there is no chance of thermal expansion & any pressure you see has to come from the utility.

Sure, if we think my overnight drip experiment, plus the fact that my PSI stays stable during the day (including late into the evening until I go to bed), hasn't taken my hot water heater as a source of this excess pressure off the table. Plus there's no sign of a check valve anywhere. But I suppose no harm in complely ruling out the water heater.

 

[Niccolo]

What cellphone do you have?

Google Pixel 4

 

[Phog]

Sure, if we think my overnight drip experiment, plus the fact that my PSI stays stable during the day (including late into the evening until I go to bed), hasn't taken my hot water heater as a source of this excess pressure off the table. Plus there's no sign of a check valve anywhere. But I suppose no harm in complely ruling out the water heater.

Apologies, I thought you were still trying to definitively determine the source. If you feel like you've proved it's for sure the utility you could skip this.

 

[Niccolo]

Apologies, I thought you were still trying to definitively determine the source. If you feel like you've proved it's for sure the utility you could skip this.

No worries! At this point, it seems very unlikely to be the water heater. But no reason not to take that off the table (including for the utility, who may try to blame my water heater).

 

[Reach4]

Google Pixel 4

https://support.google.com/pixelphone/thread/7791170?hl=en

 

[Niccolo]

https://support.google.com/pixelphone/thread/7791170?hl=en

Very cool, didn't know about that feature, presumably would make for a far smaller file

 

[Niccolo]

Very cool, didn't know about that feature, presumably would make for a far smaller file

And I'm going to have to record. Just off the phone with my water company, they can send someone out to check the pressure, but they have no way to leave a device to record it. So I'm going to need to figure out what time at night they're spiking the pressure. It sounds like they will take some responsibility if the pressure is really spiking that high, though what that will entail in practice I'm not sure. I'm guessing in the end I'll still end up having to install a PRV on my own dime.

EDIT: While water company can send someone to check the pressure, their responsibility ends there, i.e. even if they came at 3 am and it was 180 PSI, they would just recommend I address the issue.

 

[Niccolo]

Let's assume I'm going to need a pressure reducing valve (PRV) installed. (I'm going to turn off my water heater this evening to be absolutely certain the overnight pressure spikes are externally generated.)

Recommendations on PRV brands/features welcome. On the Home Depot website, I see mostly Watts and Zurn products, mostly brass.

Recommendations also welcome on installation. I've attached a picture of how water enters my home--the vertical pipe is the water supply line, coming up out of the ground. The junction is for backyard irrigation. Above that is the shutoff. And above that is a hose spigot, with a pressure gauge attached (showing my usual 53-58 PSI daytime pressure). From there, the line goes into the wall of the garage and from there through an accessible but very tight attic space above the garage and into the house.

As best I can tell, there's no logical place for a PRV inside, e.g. crawling up into that space above the garage is extremely tight quarters, and there's no other place where the water supply line is exposed. Plus if I want to protect the irrigation system from excess pressure, the PRV would need to be outside.

I'm not sure how much trouble it would be to excavate a little and put the PRV, and maybe also house shutoff, and maybe also irrigation shutoff (should the order of those be reversed?), into a valve box. That would certainly be prettier, but might lead the plumber to be grumpy/charge me more.

Advice welcome! All the feedback has been super helpful so far, much appreciated.

 

[Reach4]

You could put the PRV above the existing shutoff, or, with the city shutting off the water, you could replace that shutoff with a new quarter-turn ball valve. What kind of pipe is that? Is that copper with a bunch of paint on it?

The pipe to the bottom left feeds the sprinkler system, right? Is that running these nights? Maybe that irrigagtion cutting on and off produces pressure spikes (water hammer). You could turn off that valve the irrigation system to make sure that is not happening.

 

[Niccolo]

You could put the PRV above the existing shutoff, or, with the city shutting off the water, you could replace that shutoff with a new quarter-turn ball valve. What kind of pipe is that? Is that copper with a bunch of paint on it?

The pipe to the bottom left feeds the sprinkler system, right? Is that running these nights? Maybe that irrigagtion cutting on and off produces pressure spikes (water hammer). You could turn off that valve the irrigation system to make sure that is not happening.

Pipe is metal with paint on it (irrigation pipe is PVC).

I take it my idea of valve box seems less appealing?

Sprinklers run early morning but not every day. I could certainly shut off the sprinklers in addition to turning off the water heater this evening, if that seemed helpful to ruling out potential sources of excess pressure.