Should I Add a Pressure Reducing Valve?

[Jasesun23]

I was doing some work on my irrigation system and one thing I did was check the water pressure. The houses water pressure coming from the city is 100 PSI. Is that too high? Should I install a Watts pressure reducing valve right after the meter? I'mm reading online that 100 is too high and 60 -70 seems good. The sprinkler system even says it should be 30-50 so I might even have install a second one before that.
There is a pressure reducing valve connected to the hot water radiator system which is set to 14psi, but that is kind of its own separate closed system. I have good flow to the house, even when a faucet or shower is on the pressure only drops to 90-95 psi.

Thanks for any help in advance
Jay

 

[Dj2]

It's a good idea to install a PRV, because sometimes street pressure fluctuates unpredictably. Most irrigation systems can run on your street pressure.

We locate the PRV just as it enters the house. Inside the house pressure should be 50 to 70. A new PRV is factory set for that kind of range, nut it has a way to increase or decrease pressure.

 

[Sponsor]

 

[Reach4]

If you install a PRV, you will also need to install an expansion tank. There are pages, such as http://www.amtrol.com/support/therm_res_sizing.html , that help select the size that you need. Then set the air precharge at about 0 to 5 PSI more than what your water pressure reads while running a faucet adjusted to a trickle. That water pressure represents what the PRV is adjusted to.

 

[Jadnashua]

Plumbing code says domestic water pressure should be regulated to no more than 80psi. So, given that, yes, you should install one. As said, adding a PRV also requires adding an expansion tank to give heated water a place to expand...the PRV creates a 'closed' system, and there's no place for the expanding water to go except through the weakest link in the house (often the T&P valve on the water heater, but sometimes the toilet's flush valves, or any other leak in your system).

 

[Jasesun23]

Thanks guys that makes sense- PRV plus expansion tank

 

[Valveman]

You don't need an expansion tank if the PRV has a thermal bypass built in. This allows water to go backwards through the PRV when the discharge pressure becomes higher than the city pressure.

 

[Jasesun23]

Thats interesting. I'll have to see if any of the PRVs I'm looking at have that feature.

I'm curious right now with an open system the pressure is around 100 PSI. If I add a PRV and lower it to 60 PSI. So how much can the hot water heat increase the pressure in the system? 5-10 psi? If the system can handle 100 psi as it is now won't it be able to handle 65-75 psi without the expansion tank? And the worst that would happen is some water would come out of the T&P valve on the water heater until the pressure is lowered, right?

I have no problem installing a PRV with bypass or and expansion tank I'm just asking out of curiosity.

Lastly the pipe coming in and the water meter is 1/2 inch. The pipe inside the house after the water meter is 3/4. Does it matter if I use a 1/2 inch PRV or a 3/4 PRV?

 

[Reach4]

I'm curious right now with an open system the pressure is around 100 PSI. If I add a PRV and lower it to 60 PSI. So how much can the hot water heat increase the pressure in the system? 5-10 psi? If the system can handle 100 psi as it is now won't it be able to handle 65-75 psi without the expansion tank? And the worst that would happen is some water would come out of the T&P valve on the water heater until the pressure is lowered, right?

This would usually be limited by the T+P valve, as you say. So things that are not supposed to be seeing 150 PSI do. Sometimes a toilet valve passes water at a lower pressure even though the valve has shut off already. Some say that is not good for the T+P valve. I don't know about the toilet valve.

Recently somebody posted about a toilet fill valve that was intended to serve the purpose of draining off excess pressure. There are also separate relief valves sold for the purpose.

 

[Reach4]

http://www.watchwater.com/DOWNLOADS/data/BR/katalox_light_BR.pdf says

Katalox Light® System effectively remove turbidity from surface water, ground water and any waste water is coated with Manganese dioxide. The Katalox Light® granules have an angular shape, rough high micro-porous surface to filter water down to 2-3 microns. The rough surface and very high porosity provide a huge surface area for efficient reduction of dirt, silt and suspended solids.​

If you had other negative factors in your water that Katalox Light would take care of, that could be worth considering. That is expensive media, but it does many jobs well.

 

[Jadnashua]

The whole idea of using a PRV is to keep the pressure within code. If your incoming water pressure is 100psi, if you get one with a bypass, your house water pressure will rise to 100psi before it stabilizes at 100psi. Why people think that is a good idea, I don't know! An expansion tank would keep the pressure within a pound or two of your set pressure. Since your pipes generally do not expand under normal household pressures, ANY expansion can raise the pressure considerably. It can easily get to the 150psi that the water heater's T&P valve is set to, and that will let water out to keep it below 150psi. Again, way more than you should have in the system. Put in an expansion tank. Be prepared to replace it eventually, as the rubber bladder will fail, but they are quick and easy to replace when that time occurs.

 

[Jasesun23]

Fair enough Jim, that makes sense. What size expansion tank should I get. Home Depot has 2 model Watts. I have a 50 gallon hot water heater, the image on the back of the box says I should be good with the smaller model, the DET 5.Its 2.1 gallon with a max pressure of 150 psi. I assume I'm going to choose a water pressure of 60 PSI so the chart says the small one is the right size. The larger one is only 25 dollars more so I could get that one if needed? That model is 4.5 gallons


Do I have to install this close to the hot water heater? Or can I put int in right where I am installing the PRV next to the meter. Its about 20 feet away from the hot water heater.

thanks
Jay

 

[Reach4]

See link in reply #3 for calculator that takes the temperature rise into account. No problem going bigger.
You should not have a closed valve between the tank and the WH. You can just not close the valve unless you turn off the WH.

 

[Jasesun23]

That site says a Model 5 should be good. A model 8 maybe. But I don't need a Model 12. When deciding max water temp can I assume if I run the hot faucet for 5 mins that the temp of the water (120-125) is the max temperature. Or does it get hotter in the Water Heater?

 

[Reach4]

I am pretty sure it gets hotter in the heater. Some heaters have temperature markings, and others do not. Also some people have a thermostatic mixing device that delivers a mix of cold and hot water to the kitchen and bath to prevent scalding. Usually those would be a single unit at the water heater although they could use more than one to be nearer the point of use.

If you measure your cold water temperature, remember it will be a little colder in the winter. However not greatly colder because the pipes are buried.

 

[Jadnashua]

FWIW, after a REALLY cold spell, I've measured incoming water temperatures in my condo of 33-degrees! In the summer, closer to 70-degrees. Our frost line is fairly deep, and the water line runs through the ceiling of our basements above the insulation and drywall, so protected somewhat.

 

[parity_check]

You don't need an expansion tank if the PRV has a thermal bypass built in. This allows water to go backwards through the PRV when the discharge pressure becomes higher than the city pressure.

Many cities now require a backflow preventer with a sprinkler system to prevent polluting the water supply. You could install the PRV with bypass feature after the meter, then put in a basic backflow valve for the sprinkler. You can get a cheaper one there that isn't rated for drinking water.

 

[Jasesun23]

Hey Guys. Finally got around to installing the pressure reducing valve. Set if for around 52-56. Have two different gauges one says 52, the other 56. Pressure to the upstairs shower is good so I'm happy.

I've seen some comments about making sure the PRV is working correctly by turning faucets on full and also testing it by just turning it on so that its trickling . Would someone mind explaining what thats for and what I should be looking for?

If I go by the gauge that says its 52 psi static. When I turn on the cold faucet in the basement all the way open it drops to 42. When I turn on the faucet in the basement and the faucet in the 1st floor sink it drops to 38. As soon as I close the faucets it goes right up to 52. When I open a faucet to a trickle it drops maybe around 2-3 psi from the static 52 psi. Does this sound like its working correctly ?

I do not have the expansion tank hooked up yet. Don't know if that affects the readings I mentioned above. I'm going to try to get to that today or tomorrow. The PVR has a thermal bypass so I'll be good for a couple days till I get the expansion tank installed. After a shower last night when the hot water heater kicked on I watched the psi climb up to 95--100 which is the citys water pressure, makes me believe the bypass was working.

thanks
Jay

 

[Reach4]

If I go by the gauge that says its 52 psi static. When I turn on the cold faucet in the basement all the way open it drops to 42. When I turn on the faucet in the basement and the faucet in the 1st floor sink it drops to 38. As soon as I close the faucets it goes right up to 52. When I open a faucet to a trickle it drops maybe around 2-3 psi from the static 52 psi. Does this sound like its working correctly ?

This graph is from http://www.watts.com/pages/learnAbout/reducingValves.asp?catId=64 It may be useful in setting expectations.

I would set the precharge on your new thermal pressure tank to between 56 to 60 PSI.