Water Reduction Valves & Expansion Tanks

I posted here last week and would like to get some additional info please. My Village is kicking up the water pressure next Friday. They've given anyone who asks, a free reduction valve. Pressure is currently 40psi prox and will increase another 35 - 40 according to the Village. I was all set to solder this puppy in place when I read the brochure and saw the recommendation of an expansion tank. I know three neighbors who have had the valve installed; none added an expansion tank. These home are about 30 - 35 years old. My next door neioghbor - who built 800 homes over the past 25 years - says he doesn't think he's going to even add the valve. His house is less than 10 years old though. I'm more concerned about having a closed system with the threat of thermo pressure. I guess if I DON'T puit that valve on and pressure builds, it has releaf by flowing back past the meter. Apparently it can't do that if I put that valve on.
Q1) Is this right?
I keep my water tank at about 125 - 130. It has a pressure releaf valve on it. I'm of the opinion that most people feel the probablility of needing an expansion tank is pretty remote. Give these conditions...
Q2) Would you think they are right?
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you don't need an expansion tank on a domestic hot water heater. Don't worry your hot water heater has a relief on it.

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Maybe. Most pressure reducing valves have have a bypass to allow the pressure to equalize (if it is not clogged up). Check yours.

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I don't have an expansion tank because I turned my water heater way down to let it cool off, and then turned it up extra high and monitored the change in pressure. It never went high enough to matter, so I didn't bother with a tank. The conventional wisdom is that you need one because a) your t&p valve might not work, and b) you don't want 120 pounds of pressure elsewhere in your house. It is probably prudent to install one.
75psi isn't all that high but it is still better to use the valve and possibly a tank. If your main valve actually shuts off, it is not that much work to put it in. (I also put in an additional main shutoff as long as it was opened up; the original one is probably pretty marginal.)
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Toller wrote:

The more back up systems you add, the more chance of failure. That's a good reason for not adding a pressure reducing valve, especially when 80 psi is a normal working pressure. Your t&P valve might not work, but how many tanks blow up, how many times does the pressure get to 120 psi in a house and do the pipes explode?
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The PRV valve protects every thing in your house from being damaged by too much pressure. One thing is the rubber hoses going to your washer. Good pressure is 60-70 PSI. I would put one in, especially since they are recommending it.

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Presumably your water heater was installed with a T&P valve which will release when the set temperature or pressure is exceeded thereby avoiding a rupture. These are required in every area I've lived in and are mounted on the water heater.
An expansion tank is worth adding since it will prevent the T&P valve from opening, and spilling water, should the pressure be exceeded. I've had pressure regulators (Watts Regulator was the manufacturer) since my city saw fit to supply water at 100 psi+ rather than install adequate size water mains for years with no problems without an expansion tank.
RB
John Gregory wrote:

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John Gregory wrote:

I don't understand why you would do anything. The pressure at my house is 80 psi, check it every once it awhile when it seems the pressure is down. No expansion tank. Why do you need one? The pressure relief valve on the hot water tank takes care of protecting the hot water tank
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Welp... it's done. Got the PRV installed and - based on comments here and some common sense - I decided NOT to install an expansion tank. The PRV is set at 50. I've got 38psi now I don't think I need be concerned with anything regarding this water line INCLUDING the washing machine hoses. Both of them at the high pressure, wire mesh wrapped type anyway.
I appreciate all the help.

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The blow-off valve on the hot water tank is a safety feature. It's not designed, and shouldn't be relied on, for frequent activation. Expansion tanks are cheap insurance. Get one.
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" snipped-for-privacy@uri.edu" wrote:

What makes you think there will be frequent activations? As far as I know, the one on my new tank hasn't activated in 4 years. The previous one leaked after a few years and I replaced it and then AFAIK it was never activated. Of course it is designed to be relied on. Why would you install a safety device that can't be relied on?
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WRONG - WRONG - WRONG !!!
I just got done fighting this same battle and contacted 10 local plumbers and not a single one had the correct answer ... but they all had an incorrect EXPENSIVE answer.
The odds are that you have (or now have) either a check valve or PRV (Pressure Reducing Valve) at your water meter. That makes your house plumbing a CLOSED system. A water softener can also "close" a plumbing system as they are reluctant to "backflow". A closed system does not allow for the expansion of water heated in your hot water heater. Since "thermal expansion" is a certainty when water is heated some accommodation for the increased volume of water is necessary (and may be required by plumbing code in your area).
That can be accomplished by a variety of solutions. One, do nothing and allow your T&P valve on the water heater to "burp" the excess. That's bad for the valve and cuts it's life. Second, install a "thermal expansion tank" at the cold side of the hot water heater. This is costly, usually requires a plumber, and can be a kludge as there is usually no where to locate the tank as an after thought. Third, and a really cute answer ... go to
https://www.wattsind.com/watts/showprod.cfm?&DID=9&CATIDa&ObjectGroup_ID=2 47
This is a replacement ballcock for your toilet that incorporates a pressure relief valve set to dribble excess pressure at 80 psi. It works flawlessly. Just be careful to get the correct size for your WC tank. Their docs are vague and you must measure the height of your overflow tube from the tank bottom and get the valve which has a "CL" or "critical level" equal to or higher than the height of the overflow tube. The valve comes in 10", 11.5", & 12.5 " overall length and is usually sold only through Plumbing Supply Houses ... no Home Depot or Lowes. You can buy direct through the Watts Online Store or I have found them on the net but always at the same price. The price is a bargain when considering you don't need a plumber or an expensive expansion tank and installation.
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bud wrote:

What's wrong? my observatons? Well, I don't have a PRV, didn't even have a meter for years. Don't know if there is check valve. With all the cautioning by the water company about antisiphon valves and making sure you don't cross hook up domestic and irrigation systems, I suspect the water company doesn't believe there are any check valves either. I didn't get out my physics books to check the volume difference of 50 gallons of water at 60 degrees and and at 130 degrees. Somebody can do it, but I doubt that it is much. You open a tap, you flush the stool and the system stabilizes. When your washing machine is on, it is constantly opening a valve, so any pressure build up decreases. My system doesn't burp.
I like the idea of your system, but please don't set it at 80 psi for me, it woud be dribbling all the time, since my pressure often read 80 psi.
BTW, if you have anti water hammer devices, they will provide expansion room. But then I don't have them either. Guess I could go just go buy a pressure release that's set to 85 and stick it on an outside faucet, but don't think I will.
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He does not need an expansion tank on his domestic hot water system unless he has a circulating pump. The PRV he should install. The check valve I am guessing your talking about is a backflow only needed on the irrigation system

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I may have placed my original post under the wrong message ... sorry.
Many municipal and rural water systems have placed (or are placing) a check valve at the meter to eliminate the possibility of backflow into the water system from any home. Often this change is made without notifying the home owners or in a manner that the home owner doesn't really understand.
I recall that water heated in a water heater increases in volume about 2%. My T&P valve was "burping" about 6 ounces of water out the valve when ever the heater fired to heat the water AND only if no toilet was flushed or faucet opened (which would have relieved the excess pressure). The usual symptom is that the last person to go to bed takes a bath or shower, the water heater fires, and then no valve is opened to relieve the pressure ... the T&P valve burps. I've searched the web and found MANY people with EXACTLY the same symptoms. My water pressure is 55psi and goes up dramatically as the water heater burner fires and heats the water. I used a pressure gauge with a "tattletale" needle to record 150PSI for a split second just as the burner shut off. Odd, 150psi is exactly where the T&P valve releases. My water meter HAS a check valve AND a PRV AND I have a water softener (triple threat I guess). The Watts GOV 80 toilet ballcock that releases pressure at 80psi did the trick and took all of ten minutes to install.
As far as "he does not need an expansion tank on his domestic hot water system unless he has a circulating pump" I fail to see the sense in that statement. A recalculating pump does not increase the pressure or water volume in the system. Plumbing code (here) mandates at least one and sometimes two (for redundancy) thermal expansion devices in any new construction where the house plumbing is a CLOSED system (by check valve or Pressure Relief Valve at the water meter or by a water softener (recommended by most softener manufacturers). In fact, if you look at the booklet included with just about any hot water heater it will say EXACTLY that. It did in detail in the booklet with my A.O. Smith 50 gallon heater.I just never read it as a licensed plumber installed the heater and according to code should have added a thermal expansion device of some kind. Well, at least he left me the booklet.
If you have this problem ask your water supplier or water system IF there is a check valve or PRV at the meter. If they answer YES then check local plumbing codes and I'm sure you'll be required to install a thermal expansion device.
If you should have a thermal expansion device GET ONE. It lengthens the life of your water heater, T&P valve, washing machine, dish washer, and faucet seals. Do a GOOGLE on "thermal expansion" ... you'll be real surprised at what you find.
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We have domestic water at a pressure of about 80 psi and we have pressurized irrigation water at who knows what pressure. Many people connect both to their lawn irrigation systems because they need water between the times the irrigation system is turned off in the fall and turned on in the spring. Note: the irrigation companies were developed for agriculture and the timing of water delivery is based on agricultural needs so the needs of lawns are not really a consideration.
The domestic water delivery people are worried about contamination of the domestic water system and to a lesser extent the contamination of the domestic water at homes. They would have no worry for the system if there were check valves at each turn out.
Kevin wrote:

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You are right check valve would prevent any type of chemicals from the lawns going into the domestic water system but, check valves fail and there is no way to test them. That's why it is required by many states to install backflow preventers.

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