Replacing Pressure Reducing Valve - Questions *Fixed*

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danisrael8

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Hi all,

First time poster from Greenville SC, this might be a long one so bear with me as I want to provide as much detail as possible (cliff notes at bottom for those that are interested). A little background on my home, its a 1970's brick house that was remodeled in the mid 2000's (copper and PVC/CPVC piping, no galvanized that I can see). The water line enters the house in the basement where the PRV is located. The line is 3/4" schedule 40 PVC that reduces down to 1/2" (not sure what the line in the yard is). There is also a PRV on the cold line going to the water heater with an expansion tank right after the PRV. I will post pictures below.

The problem, to make a long story short I believe my PRV's are bad. I bought a water pressure gauge and tested an outdoor spigot at 120 PSI. So I adjusted the PRV down to 70-80 PSI, tested a few faucets (one at a time) and everything seemed fine.

The next morning I found out that whenever two water sources are in use, the pressure drops drastically. I checked the pressure static and saw 80 PSI like I had set it to however when I opened a faucet, it dropped to 25 PSI and when another source was in use it dropped to 20PSI. I also noticed later that day when the water heater was heating, the pressure on the cold side spiked to 120-130 PSI. I checked my expansion tank and it was full of water. When I shut off the cold supply to the water heater the pressure went back down to 80PSI at the spigot however I am still getting a pressure drop when the water is used.

It seems like it would be best to replace the water heater's PRV with the same unit, unscrew the union and replace.

For the main line being glued PVC, what would you recommend I do if I wanted something that was more easily removable if the PRV were to fail again (unions, PEX, Sharkbite?) or should I stick to glue and PVC. Either way I plan on adding a pressure gauge after the PRV. Is this something the weekend warrior could accomplish or should I call in an experienced professional? I enjoy learning new things but not at the cost of risking major damage.

Cliff notes:
  • High water pressure (120 PSI) adjusted down to 80 PSI
  • Pressure drops drastically when faucet opens (80 down to 20 - 25 psi)
  • Pressure increases drastically when water heater is in use (80 to 130 psi)
  • Shutting water inlet to water heater drops pressure down to 80 PSI but pressure drop still occurs when faucet is open
  • Expansion tank is bad and will be replaced
  • Best way to replace PRV glued with PVC?
Thanks for taking the time to read!

Dan

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pressure-gauge-hosebib.jpg
 
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Jadnashua

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Is that PVC labeled DVW? If so, it's not designed for pressurized water.

Pressure dropping implies a restriction, and it's probably one of the PRVs. The pressure will spike if your ET is bad when the WH runs after hot water use. Hard to resolve the setup until that's replaced.
 

danisrael8

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Is that PVC labeled DVW? If so, it's not designed for pressurized water.

Pressure dropping implies a restriction, and it's probably one of the PRVs. The pressure will spike if your ET is bad when the WH runs after hot water use. Hard to resolve the setup until that's replaced.

Thanks for taking the time to reply. I'm pretty sure it's not DVW the markings are showing PVC 1120 Sch. 40 PR 480 psi. What are your thoughts on cementing PVC vs pex or sharkbite?
 

hj

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That PVC inside the house, especially at the water heater, is a disaster waiting to happen. It appears that there is some CPVC which is proper for indoors and hot water. Replace the PRV, and unless you have an unusual piping system, you do NOT need the one at the water heater.
 

danisrael8

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That PVC inside the house, especially at the water heater, is a disaster waiting to happen. It appears that there is some CPVC which is proper for indoors and hot water. Replace the PRV, and unless you have an unusual piping system, you do NOT need the one at the water heater.

Yeah theres a lot of mixed piping going on which doesn't give me the warm and fuzzies. I also wondered why they put another PRV on the water heater when there was already one on the main line. Should I focus on the main line PRV and the expansion tank and leave the water heater one alone? Or should I just replace both PRV's and set them to the same pressure? Thanks for your input.
 

Reach4

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The line is 3/4" schedule 40 PVC that reduces down to 1/2" (not sure what the line in the yard is).
That necks down to 1/2 inch CPVC. That is not enough. 1/2 inch CPVC is significantly smaller inside than 1/2 inch copper, but bigger than 1/2 inch PEX.

Your pipes should be better supported. I would put a place to put a pressure gauge before the PRV if you change out the PRV.

So is the problem the PRV? Maybe watch a pressure gauge at the outside faucet behind the wall in your picture. If that pressure drop is not nearly the pressure drop that you see upstairs, the problem may not be the PRV.
 

danisrael8

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That necks down to 1/2 inch CPVC. That is not enough. 1/2 inch CPVC is significantly smaller inside than 1/2 inch copper, but bigger than 1/2 inch PEX.

Your pipes should be better supported. I would put a place to put a pressure gauge before the PRV if you change out the PRV.

So is the problem the PRV? Maybe watch a pressure gauge at the outside faucet behind the wall in your picture. If that pressure drop is not nearly the pressure drop that you see upstairs, the problem may not be the PRV.

Thanks for the input! So would the 1/2" line cause the pressure drop issue? I read online that could be a bottle neck point. Good idea on the pressure test at the spigot after the prv I'll try that tonight and report back. Agreed on the lack of support, I was planning on bracing it after changing the prv out as I figured a gauge (or two) would add more weight and need to be supported.
 

danisrael8

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So is the problem the PRV? Maybe watch a pressure gauge at the outside faucet behind the wall in your picture. If that pressure drop is not nearly the pressure drop that you see upstairs, the problem may not be the PRV.

I tested the spigot right after the prv and saw the same pressure drop to 25 psi. I have ordered a new prv for the water heater and main line. Does threading pvc onto the prv require glue or just tape?

Thanks for everyone's help so far,
Dan
 

Reach4

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Does threading pvc onto the prv require glue or just tape?
No glue on the threads, but tape can be improved by also using a pipe compound such as Rectorseal T plus 2.

Did you order the same model number? Is that a LF25AUB-Z3?

I should have asked before, but some PRVs have a strainer screen. Does yours? Looks like it. Maybe cleaning the screen would have reduced your pressure drop a lot.

watts-prv-cutaway.jpg
 
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Cacher_Chick

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A single bath home uses 3/4" copper size piping as the main trunk line, and smaller 1/2" line taps off that to feed individual fixtures. You might have a problem with your pressure, but you will never achieve proper flow rates with the bottleneck in the piping system.
 

danisrael8

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No glue on the threads, but tape can be improved by also using a pipe compound such as Rectorseal T plus 2.

Did you order the same model number? Is that a LF25AUB-Z3?

I should have asked before, but some PRVs have a strainer screen. Does yours? Looks like it. Maybe cleaning the screen would have reduced your pressure drop a lot.
lf25aub-z3-0009309-cutaway-psd

Thanks for the heads up on the thread sealant. I'll pick some up. I ordered the same PRV (LF25AUB-z3) for the water heater and a Wilkins NR3XL which superceeds my BR4. I havent cleaned any strainer but I can check if there is one. Thanks for all your help!
 

Reach4

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I can't think of a reason to have one for a WH.

If you find a clogged screen, we want a photo.
 

danisrael8

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A single bath home uses 3/4" copper size piping as the main trunk line, and smaller 1/2" line taps off that to feed individual fixtures. You might have a problem with your pressure, but you will never achieve proper flow rates with the bottleneck in the piping system.

Thanks for the info, I figured it would be a bottleneck. However before when the pressure was high we didn't mind the flow so I dont think we will be upset if the flow stays the same. We just miss the pressure!
 

Treeman

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Another mistake I see as a diy'er is near the water heater plumbing. It appears that you have male metal threads going into plastic female connectors. It should be plastic male threads into metal female to reduce chance of breakage.

For some reason, I have a "feeling" that a pro would do your setup completely different.
 

Jadnashua

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People confuse pressure and volume all of the time. A 1/4" line will have the same pressure as a fire hose when fed by the same source and no flow. A fire hose will deliver lots more water with less pressure drop than the soda straw. But, the smaller the pipe, as you raise the volume flowing, the internal friction will drop the effective (static) pressure at the outlet since it can't keep up. Any restriction will drop the dynamic pressure at the outlet.

If the static pressure isn't right, or it drops significantly when the piping is adequately sized, then the PRV would be suspect.

PVC pipe tends to get brittle as it ages. More so if it is exposed to UV, which is why when used, it is used buried outside. It doesn't really like high temperatures, either, and generally, is only spec'ed for cold water. I'm not a great fan of CPVC, but it is specified for both hot and cold use in a home. Maybe less likely to get gnawed on by mice, but still prefer pex if you can't use copper.

As to the dual PRVs, two possibilities...some PRV designs have a limited maximum deviation from inlet to outlet, and you may need to step the pressure down verses being able to do it in one device. Or, they may have wanted higher pressure to say the outside hose bibs than they did for the rest of the house, which is why they chose two. Or, they just didn't understand what and how to use one properly!
 

danisrael8

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Another mistake I see as a diy'er is near the water heater plumbing. It appears that you have male metal threads going into plastic female connectors. It should be plastic male threads into metal female to reduce chance of breakage.

For some reason, I have a "feeling" that a pro would do your setup completely different.

I agree regarding the comment on how a Pro would do it. Eventually I would like someone to redo the plumbing and convert over to Pex since we have fairly good access to all the pipes. Running a manifold system should be pretty straight forward. However with a baby on the way that will have to wait.

I thought the same as you regarding the male/female connections, after further inspection the previous owners used a CPVC adapter with a male thread insert already attached. So while not being ideal I think it should be okay as its metal on metal. It looks like this:

kbi-couplings-adaptors-tms-1250-64_1000.jpg
 

danisrael8

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If the static pressure isn't right, or it drops significantly when the piping is adequately sized, then the PRV would be suspect.

As to the dual PRVs, two possibilities...some PRV designs have a limited maximum deviation from inlet to outlet, and you may need to step the pressure down verses being able to do it in one device. Or, they may have wanted higher pressure to say the outside hose bibs than they did for the rest of the house, which is why they chose two. Or, they just didn't understand what and how to use one properly!

So you think the pipe size reduction is the culprit for the large pressure drop or maybe an additional factor? What would you recommend the pipe size be? Like I said in my last post one day we will upgrade the plumbing over to pex so I would like to make sure the person we hire does it right!

Regarding the PRV's I think they were too lazy to fix the first failed PRV and added a second one somewhere else but that's just speculation. We'll see if anything changes when I replace the main line PRV and add a pressure gauge before and after to see what incoming is and what it is reduced to.
 

Jadnashua

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If you're going to redo some of the piping, and you don't use that first PRV for the outside hose bibs, and the second one to feed everything else, I'd just cut out that first PRV and replumb stuff with at least 3/4" material from the meter in. A 1" line, if you have more than one bathroom wouldn't hurt, either.

A 1/2" line is fine for one, maybe two fixtures, depending on what they are. Trying to feed more than that at any one time with a 1/2" line means either excessive velocity is required or significant dynamic pressure losses.

A failing PRV can limit the flow, and, with a moderate flow, cause the pressure to drop.
 

danisrael8

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If you're going to redo some of the piping, and you don't use that first PRV for the outside hose bibs, and the second one to feed everything else, I'd just cut out that first PRV and replumb stuff with at least 3/4" material from the meter in. A 1" line, if you have more than one bathroom wouldn't hurt, either.

A 1/2" line is fine for one, maybe two fixtures, depending on what they are. Trying to feed more than that at any one time with a 1/2" line means either excessive velocity is required or significant dynamic pressure losses.

A failing PRV can limit the flow, and, with a moderate flow, cause the pressure to drop.

Unfortunately I believe there are some faucets that are fed by the main cold line before it goes to the water heater. As it goes up, it takes a left to a basement bathroom and right above that is a kitchen sink. The water heater cold line comes through the middle of the house floor. For the time being I think replacing the main line PRV and seeing where we stand would be best until we can save to correctly re-plumb everything. I really appreciate your help!
 

danisrael8

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First off I want to thank everyone for their help so far.

What would the best method be to connect a 1/4" NPT water pressure gauge to PVC?

My game plan was to put a 3/4" slip x 3/4" slip x 1/2" female threaded tee and use a brass 1/2" male x 1/4" female bushing to screw into. But this brings up the problem of using male pvc into female brass. See my poorly drawn drawing lol. Then I thought about adding a shut off valve for each and wasn't sure how to tackle this (is this overkill?). Is there a better way to do this?

Plan.jpg
 
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