Home water pressure 120 psi...

[Confoozled]

Hi all -

I was getting ready to do some work on the water heater pipes when something I read skimming threads here made me think to check my water pressure.

I'm getting 120 psi inside (utility sink) and outside (hose bib). Rut-Roh. I'm in a hilly neighborhood at the bottom of moderately-high hill. The pressure dips to 55 with another tap full open. I'll borrow someone else's gauge just to make sure mine isn't bonkers. Meanwhile...

In the basement is an adjustable Watts pressure reducing valve (photo - pretty much what's available today; output psi adjustable 25-75) between my in-house shut-off and the one outside in the buffalo box. It's original to the house, so a bit over 20 years old.

Some questions. I generally fear that an old valve that hasn't been nudged in 20 years may leak if I try to adjust it. Is this a valid fear?

Second, if the output on this PRV is adjustable from 25-75 psi and I'm getting 120 psi downstream of the valve, then is it likely it is completely shot (no longer adjustable) anyway?

Also, if you've ever tested a system with fairly high pressure, would you expect the pressure to drop by half when a tap is opened? Or does this indicate some issue in addition to a (potentially) faulty pressure reducing valve?

Many thanks for any guidance, and finally, apologies if this should be in a different forum. I scanned through them but didn't see one more relevant.

 

[Reach4]

There may be a rebuild kit. Get the model number from the tag.

Also you need a working thermal expansion tank for the water heater.

 

[Sponsor]

 

[Phog]

If the pressure is much lower after you open the faucet, there are generally two things that are likely to cause it, in this order. #1 - thermal expansion from a hot water tank (as Reach mentions above). #2 - PRV leaking through.

You might be able to diagnose the problem by shutting of your main service valve. Run enough hot water from any faucet to get your water heater to kick on. Then, shut the main service off (and keep all the fixtures in your house tightly shut). If pressure still slowly rises to to 120psi then it's thermal related & you need to install a thermal expansion tank (or replace your existing one, they lose their ability to function when they get old).

However one caveat. If your main service shutoff valve doesn't seal 100% tight then it will allow pressure to bleed through from the city mains. So you could get a "false positive" on thermal expansion. Gate valves are notorious for allowing a slow leak. If this is the case then do the reverse of what I just described -- turn off the water heater & see if the pressure still rises even with no heat.

 

[Sylvan]

Replace the PRV and set the pressure to no more then 40 - 60 PSI
40 PSI will elevate water to a height over 92 feet (neglecting friction loss)

The more pressure the more chance of causing erosion of copper tubing because of excessive velocity and hydraulic shock (water hammering) and the need for an expansion tank

 

[Sylvan]

“Gate valves are notorious for allowing a slow leak. Ball valves usually seal up rock solid."


Then why do we use Gate valves on high pressure steam and OS&Y valves on fire suppression systems?

Possibly because it allows full flow and is considered a positive shut off ?

When speaking of "gate valves" it would depend which type of "gate " is being used

Such as double disc or the wedge type

What material is used for the gate valve possibly Stainless steel is a great gate valve still offering full flow and less chance of causing hydraulic shock because it is slow closing

Then there is rising stem and non rising stem which gives a visual view of the gate fully open or closed

 

[Phog]

Sylvan -- just speaking from experience here. When I'm trying to solder onto an existing copper pipe and the upstream shutoff is leaking through, and I have to plug the pipe with some bread to keep the drops away and complete the joint, it's invariably a gate or globe valve that's leaking. I can't recall ever having had that problem with a ball valve. Any type of valve can leak of course, but when a slight leak-through will give false troubleshooting results, it's worth mentioning.

 

[Sylvan]

A lot of installers do not nstall the valves properly ( vertical) and once installed they are never shut unless there is a leak and lack of being maintained causes them to fail

Also a lot of times people use a GV for throttling

When installing a blow down on larger boiler I like to use a gate and a ball valve The Ball allows for a quick blow down to clean the bottom of the boiler and the gate being closed first prevents hydraulic shocking

 

[Jadnashua]

Our condo complex has a pump station and a couple of booster pumps for fire fighting. There are some gate valves on the large pipes. They may not get cycled for many years. Last time we needed them, they would not close. Luckily, there are some check valves so each pump can be used separately. We used them to access the pipe, cut out the sections, and replaced the valves with instructions to cycle them periodically. FWIW, over about 30-years, the bottom of the 6" CI pipes had about a 1" accumulation of sediment that had solidified and that's what kept the valves from closing. At least annually, the fire hydrants would be opened and full flow to try to flush the lines, but apparently, that was not enough.

 

[Sylvan]

When I do a yearly sprinkler / stand pipe test I remove the locked chain and close the valves and open them several times to make sure the disc does seat properly .

Then lock the valve handle in the open posititon . Open fully and a 1/4 turn back


These are the types of valves we have been using on fire suppression systems

 

[Sylvan]

For the water mains we still use

 

[Sylvan]

Here is a 4" water main valve (gate)

 

[Sylvan]

More pictures of gate and ball valves

 

[Phog]

Now that's some big valves!

 

[Confoozled]

Thanks everyone for your helpful inputs; I also enjoyed the side discussion on valve types and found it educational. I haven't done any work today what with Easter and a family birthday but will get back at it tomorrow - both the original work I'd planned, the testing described by Phog, and I did get a new expansion tank as Reach4 mentioned.

As it relates to the home pressure reducing valve, I searched and although several outlets looked to have a rebuild kit from the search hits, once I went to their individual webpages it was out of stock/no longer available. This was a 3/4 inch Watts N35B and appears to have been discontinued 10 or more years ago. I found old images and learned it came with union fittings on both ends and also internal/female threads on both ends.

I'm posting what I hope is a clearer photo of the PRV. I'm not positive what I'm looking at but it looks to me that the installer used the union fitting on the inlet, but then threaded something into the outlet side female threads and sweated the joint from there.

If my description is correct... any idea why an installer would use the union fitting at the inlet, but then go ahead and sweat the joint at the outlet instead of using the union fitting? Why not use the unions on both? (One guess is, maybe just lost the O-ring and worked around that issue?). Anyway, it would have made my replacement work a lot easier if there were union fittings on both ends because there are new versions of this PRV with the same length dimension inlet-to-outlet. This thing is mounted about 7 feet high up in the corner of a tiny closet.

Thanks again for all the helpful advice.

 

[Reach4]

Get the model number from the blue tag. Maybe take a photo of the tag from below.

 

[James Henry]

Theirs only one union because a lot of PRVs are made to thread into a male adapter on one end. Unless you can find a PRV with the same dimensions your going to have to sweat some copper.

 

[James Henry]

After taking a closer look at your photo you will have to sweat some copper.

 

[Oberin]

Speaking from experience. When I try to solder an existing copper pipe and the inlet stop valve leaks. And I have to plug the pipe with bread to keep it from dripping and complete the connection, the shutoff valve or ball valve always leaks. I don't remember having that problem with a ball valve. Of course, any type of valve can leak, but when a small leak gives false results when troubleshooting the problem, it's worth mentioning. And it's better to find out from the professionals at home if they can give tips for the home. They will be able to help with this much better.

 

[Sylvan]

When I try to solder an existing copper pipe and the inlet shutoff valve leaks.

If you have a slow drip and you use Hercules sold /flux combination as a flux and use a turbo torch tip normally this will work to make a strong leak-proof joint also add more solder once the flux turns bright

 

[Reach4]

When I try to solder an existing copper pipe and the inlet shutoff valve leaks.

There are copper press valves that can be installed by somebody with the right tool. Those can be installed on a wet pipe.

Sharkbite valves and PRVs can be installed on wet pipes without tools.

There are Sharkbite PRVs. There are Sharkbite "slip" PRVs that can insert into a copper pipe length.

Similarly, there are slip and regular Sharkbite ball valves.