Pressure relief valve

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What is the purpose of the pressure relief valve that is installed in the water line coming into my house. It is on my side of the water meter. There is some sort of an adjustment on the end of it and an opening for water to escape on the bottom of the device. Does it actually control the pressure coming into the house? If so, how can I adjust it to cut the pressure down in my house. I have called the water department and they have assured me that it is my problem because "our pressure is always correct". Water does come out of the relief valve from time to time and gets things wet in the area it is in. The "plumber" at Home Depot said to put a plug in the hole to stop the water from coming out. I have noticed that the pressure is higher in the mid afternoon. Probably cause no one is home in the neighborhood. I don't know what the actual pressure is because I don't have a meter in line. Anybody have any ideas? Chuck B.
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Sounds like an atmospheric vacuum breaker

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A pressure relief valve at the main water valve is left over from the days when they were not required on water heaters. As the water heater heated the water and it expanded it would pop the relief valve rather than blow up the house plumbing.
These days water heater manufacturers must install relief valves right on the heater. Plus, many communities require an expansion tank near the WH to absorb the expansion.
Some cities also required a one-way check valve to prevent the expansion from forcing your water back into the city's water supply. That prevents your house from contaminating the entire community if something goes wrong at your place.
You have two choices depending on what your city requires these days. You can either remove the valve and cap off the opening. Or you can replace the valve with a new one. Of course, that assumes that you already have a relief valve on the water heater.

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Rick-Meister wrote:

Not talking about the prv on the water heater. That is working ok. This prv is in line as water pipe enters the house. CB
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Water heaters require a T&P valve (they open to excess temperature AND pressure) A standard one is 210 deg/150 psi.
p_z
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I'd venture to guess this is an older house and that PRV is now superfluous.
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On Feb 7, 9:02pm, snipped-for-privacy@snyder.on.ca wrote:

Not if it is also a Pressure REDUCING Valve. If the city system pressure is much over 60psi then I would replace it with a modern one (and install a surge tank).
Sorta OT but the PRV drain on the water heater should be routed to a safe drain.
Harry K
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On Feb 7, 9:02pm, snipped-for-privacy@snyder.on.ca wrote:
BIG SNIP

I think that since the OP has an adjustable PRV it is NOT superfluous.
My parents house has a PRV just outside the house, kitchen sink. The house was built in 1959 and in those days water heaters (in SoCal) did not have TP valves. In this case the original PRV is superfluous.
In my house I installed a Watts pressure reducing valve & a Watts dual check valve (backflow prevention), the city only requires hose bib vacuum breakers but my plumber & I figured "what the hell, let's do the whole house".
Thus I have a closed system......I throttled the city water pressure down to ~65 psi from about 75+ to reduce water hammer effects. Jay R. Smith Mfg. Co suggests in their tech info on water hammer to make sure that water pressure is 65 psi max.
I did as they suggested; distributed water hammer arrestors & 65 psi max and water hammer is not evident. But now I no longer have "firehose" performance on my garden hoses. : (
I chose not to install an expansion tank per discussions with my plumber, I installed a 75 psi PRV to allow the ~.5 gallon (max) daily water. Unfortunately the occasion quick shutoff (ball valve garden hose or lawn sprinkler valves) cause the 75 psi PRV to activate & the 65 psi city pressure would not allow a re-seat.
I replaced the 75 psi PRV with a WATTS 530C 3/4" ADJUSTABLE PRESSURE RELIEF VALVE. By boosting the relief pressure to about 85 psi I get thermal expansion relief but no "gushing dump".
I believe that this long explanation may describe the OP's circumstances and why his adjsutable PRV should NOT be plugged. It appears as though it is serving to relieve the thermal expansion in his house since "Water does come out of the relief valve from time to time and gets things wet in the area".
but who knows?
cheers Bob
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Chuck wrote:

Sounds like ht is pressure regulator which is malfunctioning. Usually pressure is ~60 lbs.
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How about a photo of it and all the hardware at the service entrance at your house?
How old is your house & was the plumbing system ever updated to modern spec? Do you have a pressure regulator?
http://cgi.ebay.com/NEW-WATTS-3-4-WATER-PRESSURE-REDUCING-REGULATOR-VALVE_W0QQitemZ380100139938QQihZ025QQcategoryZ42932QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Does you system have a back flow preventer ? Dual check valve? Is is a sealed / one way system? Do you have an expansion tank?
If you have a "sealed" system (ie no back flow allowed) and do not have an expansion tank......the relief valve will dump water on occasion to prevent excessive pressure in your domestic water plumbing due to cold to hot water expansion. When you water heater is refilled with cold water & that water is heated...it expands. If you have back flow prevention system you need an expansion tank OR a relief valve.
Does the relief valve look like this?
http://www.wscdirect.net/servlet/the-1913/WATTS,-530C,-1-fdsh-2%22,-ADJUSTABLE,/Detail
If you're only dumping a few gallons per day (SWAG) I'd say everything is working fine.
Why do you think your water pressure is too high? Get a water pressure gage at the hardware store & mount it on a convenient hose bid...check & log the pressure.
cheers Bob
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First you should realize the plumber at home depot is an idiot. The device is just a pressure regulator. The city pressure is most likely is to high it might fluctuate at times. It could also be caused by thermal expansion hot water will expand can cause the pressure to raise . The water is just pressure being released the adjustment nut dose regulate the pressure best bet is to leave it alone. you could check the pressure at a hose bib a plumbing supply could set you up. I would not be to concerned unless it's blowing off a lot of water the PRV might need to be replaced .
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I was under the impression that pressure reducing valves for domestic water supplies do not dump water overboard. The Watts units I have installed reduce water pressure to the house but dont dump any water.
Pressure relief valves do dump at times. PRV can be instead of expansion tanks (depending how your local folks prefer it done) or they can be vestigial PRV's from when TP valves did not come standard on water heaters.
Per Sac Dave's comment I would suggest that the OP not simply plug the output.
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That's right they don't. If they relied on dumping water, just think what that would mean. If it was set at 60 and the municipal supply went to 65, how much water would it have to dump? Potentially, it could spew water all day. Plus, there is no need to dump water to regulate pressure.
The Watts units I have

I wouldn't either, at least until he understands exactly what he has. Picture? Manufacturer's name, markings?
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Sac Dave wrote:

Thanks for your sensible answer. I am in South Fl. so heat expansion is a possibility. I will check the pressure at the hose bib. (had not thought of that option.) CB
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It may be, as suggested earlier, a combination Pressure RELIEF and Pressure Reducer. That is the only way I can see it having both an adjusting screw (moder Pressure Reliefs don't have one) and an overboard dump.
Checking the pressure at a hose bib you have to be sure the hose bib is prior to the PRV to get system pressure and then after the PRV to get house pressure.
To avoid the water "leakage", replace that vavle with a new one but you will need to install a surge tank also as the new PRV will not allow reverse flow.
Harry K
Harry K
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Harry K wrote:

Hose bib is after the PRV. I will post the model and or name of the device latter today. To describe it better: It is T shaped. Right T bar is dial with knarled knob. Left T bar connects to main water pipe (incoming water). Bottom of T is open, threaded (female) where water drips out fairly fast.
male thread ---------------------------- knob water / / / /
opening with female threads Hope this helps CB
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What I did at my house is put a prseure gauge on one of the hose bib after the PRV I was getting 80psi if you watch the psi will raise very slowly Thermal expansion. If you check your pressure you will need to get some fittings, P-gauge as I said earlier a plumbing supply could set you up but maybe the local water department might check for free. Some PRV blow water off there basically a safety device to keep you from having problems with Water closet and fixtures in your house. I have also piped waste lines from PRV to drains and floor sinks ( mostly in high rises were booster pumps are used) I really don't think you have a problem if you do notice you water closets running your pressure might to high then you might need to adjust the PRV . Now if you do get a gauge to test your Pres. you want to check the pressure when you using water mines at 80psi but when the water is running it drops down to about 60PSI.
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No such thing exists...
You have to install a drain valve in close proximity to the main shut off but between the main and the fixtures and then go around and open the valves on each fixture supplied by the plumbing to get all of the water out of the lines...
Don't forget to pour Propylene glycol in the drain traps as those can freeze and cause leaks too...
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Inquiring minds want to know why is this is necessary? What it takes to completely drain any water system is going to depend on what all there is to drain and how it's piped. At the very least, you need to not only open a valve at the lowest point, but also faucets or other ways for air to enter at the high points.

At least no ready made, practicl thing, that's for sure.

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On Sun, 8 Jul 2012 08:29:23 -0700 (PDT), Evan

sprinkler systems. Flomatic also makes one for domestic water systems. The Flomatic model 70 will likely do your job and they are reasonably priced.
Then there are the Ogontz antifreeze valves that are temperature actuated and drain when the temperature approaches freezing.
The sprinkler system valves are quite commonly used in "seasonal" trailers andcabins.
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