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?
Maybe. Most pressure reducing valves have have a bypass to allow the
pressure to equalize (if it is not clogged up). Check yours.
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
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.)
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?
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
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.
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
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.
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?
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
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.
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
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
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
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
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
to bed takes a bath or shower, the water heater fires, and then no valve is
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
dramatically as the water heater burner fires and heats the water. I used a
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
HAS a check valve AND a PRV AND I have a water softener (triple threat I guess).
Watts GOV 80 toilet ballcock that releases pressure at 80psi did the trick and
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
the booklet included with just about any hot water heater it will say EXACTLY
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
added a thermal expansion device of some kind. Well, at least he left me the
If you have this problem ask your water supplier or water system IF there is a
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
water heater, T&P valve, washing machine, dish washer, and faucet seals. Do a
on "thermal expansion" ... you'll be real surprised at what you find.
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
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.
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
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