Question re: Pressure on Top Floor and PRV

[Mawst95]

Hi all-

I've read some threads here about PRVs, and I wanted to get some advice before proceeding. Moved into a house last year. There was a spin down filter installed right off of the service entrance. You could bypass the filter as you'd expect. The issue was the filter setup also bypassed the PRV. Our inspector missed it, but plumbers that came through for other issues pointed it out as problematic. So we had a plumber fix it, installing a new filter setup that didn't bypass the PRV.

The mistake we all made is we didn't check the pressure on the third floor bathroom after doing this. We recently checked it and it's a drizzle. When I screw the PRV adjustment clockwise (Zurn 70XL 3/4) nothing changes pressure wise. Although we have city water, the water is heavy in sediment (hence the filters). The date code on the PRV says 1901 (I'm assuming that's 2001?). The house was built in 1937. Pipe coming in from the outside is copper--I assume 3/4. House is 3200 sq ft with 3 full baths and 2 half baths. There are only 3 of us in the home.

Some other information: The filter setup looks like this --- Service pipe->PRV->gauge->spin down filter 1->spin down filter 2-->pressure gauge-->10x24 sediment filter-->pressure gauge 3--home. As I said you can bypass the filter setup (but no longer the PRV). The first gauge after the PRV reads 42psi. The two gauges after the filter setup starts read 60psi. When the water heater was replaced the expansion tank was also replaced. The water heater is 50 gallons, the expansion tank is 2.1 gallons (smaller than what was there previously I believe) and it says its "precharged to 40psi".

My suspicion is the PRV is gunked up with sediment and is restricting the flow more than ideal and the adjustment isn't working. The plumbers are coming back next week. I know the pressure WITHOUT the PRV is sufficient on the third floor, but obviously I don't want to go without a PRV. I did look at the rebuild kit--they are $90 (a deep 1 3/8 socket is $14); a new PRV is $100-150-ish. I'm expecting a quote in the 500-700 dollar range from the plumber *if* the PRV just needs to be replaced. I also don't know if the water heater replacement is having an effect so I figure having the plumber come out is a better option.

Any thoughts or advice or questions I should ask the plumbers?

 

[wwhitney]

The first gauge after the PRV reads 42psi. The two gauges after the filter setup starts read 60psi.

This part makes no sense. The three readings should be the same when there is no flow. When there is flow, the differences between the readings tell you how gunked up the filters are, with the pressures getting lower as you go downstream. Maybe the first gauge is faulty. Monitoring the 3rd gauge (assuming not faulty) while there's flow in the system will tell you what pressure drop the filters + PRV are causing. And if the observed drop seems excessive for the filters alone, then that's evidence of a problem with the PRV.

BTW, what is the pressure upstream of the PRV, is it really needed?

On the 3rd floor pressure, there's a loss just due to elevation. If there's a shower head 3 stories up and also higher relative to the floor than the gauges, it could be ~34' higher, which would be ~15 psi. So with the PRV set to 60 psi (in which case your expansion tank should be adjusted to 60 psi ish, I think, assuming the same elevation), you'll get at best 45 psi at the shower head, with no flow. But hopefully that will suffice once you get everything working.

Cheers, Wayne

 

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[Mawst95]

Hi Wayne,

I agree that the 2nd and 3rd gauge reading higher than the first is weird and doesn't make sense. I put the gauges in for the exact reason you said--to indicate when the filters are clogged. It didn't make sense to me at the time. The plumber noted it and basically said "huh" and didn't suggest anything, if I recall correctly.

Unfortunately the PRV piping fix, the addition of the filters, and the new water heater all happened prior to checking the pressure so it could be one or more of those changes that are creating the problem.

I'll ask about the weird gauge readings when the plumbers are here. Maybe I'll ask them to take out gauge 2 (in between the various filters) and use it to replace the first gauge (rather than buy a new gauge). FYI I'm using Winters PFQ805LF gauges.

I didn't put a gauge ahead of the PRV. It looks like the shut off valve upstream of the PRV has a connector that I *think* is for adding a gauge? As for whether it's needed. My understanding is cities can increase the pressure unexpectedly and that can be a real problem (leaks, premature wear of appliances, etc.) It may also be needed for code. I'm in Baltimore city FWIW.

 

[Fitter30]

Gages can and do go bad. Every devise has a pressure drop filters and prv that can range 5 to 10 lbs. Filter vary with what type of element and prv with the flow rate. Check the aerators at faucets and check shower head if the aeraters are dirty. Changing water heater can stir up dirt and get trapped.

 

[Jadnashua]

The house I grew up in, built in the early 1950's, had a 1/2" water supply line. THat by itself could cause pressure drops when you were asking it for any volume.

Depending on the sediment particulate size and the filter used, that could clog up fairly quickly, dropping the dynamic pressure.

The inlet orifice of a gauge isn't all that large, and sediment can affect the reading.

PRVs don't last forever, and they do have an inlet filter screen...you might want to check and likely clean that. Crud can affect the seals of the PRV, and unless your pressure gets over 80-psi, you don't necessarily need one anyway. If the area has been built up significantly since it was installed, and the utility hasn't upgraded their distribution system, the overall local system pressure may not be as high as it once was, either.

 

[Mawst95]

The house I grew up in, built in the early 1950's, had a 1/2" water supply line. THat by itself could cause pressure drops when you were asking it for any volume.

Depending on the sediment particulate size and the filter used, that could clog up fairly quickly, dropping the dynamic pressure.

The inlet orifice of a gauge isn't all that large, and sediment can affect the reading.

PRVs don't last forever, and they do have an inlet filter screen...you might want to check and likely clean that. Crud can affect the seals of the PRV, and unless your pressure gets over 80-psi, you don't necessarily need one anyway. If the area has been built up significantly since it was installed, and the utility hasn't upgraded their distribution system, the overall local system pressure may not be as high as it once was, either.

I do notice hammering(?) when turning on the upstairs shower. I don't notice that on any other bathroom.

 

[Jeff H Young]

I'm only guessing but
I suspect you still have old piping buried in walls. 1937 been repiped? or needs one.

 

[Jadnashua]

You may have some galvanized piping in that old house. Over time, that stuff rusts out from the inside out. It happens faster on the hot side as most chemical reactions tend to happen faster when hot. That can severely restrict the flow as the rust narrows the opening down until it rusts through and leaks.

Many people get confused between pressure and volume...you need enough volume on a showerhead to get the nozzle to speed the flow up (Bernoulli effect). Otherwise, it's more like a rain head. If you capped the shower arm with a pressure gauge, you'd probalby find the pressure is decent, but the volume is low. You could leave the head off, take a bucket, and measure the volume you get out of the shower arm. If it's not greater than 2.5gpm, you'll not get any speedup through the nozzles as the larger supply volume tries to force its way through...that's what causes it to speed up. Friction limits that, which is why it restricts the volume, but you need that for a decent shower plus enough pressure.

 

[Jeff H Young]

Without more info sure sounds like friction /restricted lines perhaps old rusted semi closed off

 

[Mawst95]

Without more info sure sounds like friction /restricted lines perhaps old rusted semi closed off

So I took off the shower head and faucet aerator in the bathroom and the flow restricter in the shower and the aerator (restricter?) in the faucet had a thick layerer of coarse sediment. Without the fixtures both seem to be moving a fair bit of water. I have the fixtures soaking in 50% vinegar and I'll put them back after 8 hours or so. I'm optimistic this will help fix the issue.

 

[Jadnashua]

If the shower head is filled up with rust particles rather than mineral deposits, vinegar won't help, but it won't hurt. You may need a new showerhead.

 

[Mawst95]

If the shower head is filled up with rust particles rather than mineral deposits, vinegar won't help, but it won't hurt. You may need a new showerhead.

That's what I figured.

In any case after rinsing everything and reassembling the pressure is good! I may reinsert the flow restricter -- it was a green moen doodad.