oil-fired water heater - safety valve

Larry Weingarten

... what function does that check valve serve? I'd be tempted to remove it rather than add an expansion tank, particularly since pressure is 43 psi. If heat travelling back up the cold line is a problem, install a heat trap....or maybe just drill a small hole in the flapper of the current check valve to allow for thermal expansion ;~)

Yours, Larry

Frank M. Tricarico

Hot Water Heater -Safety Valve Releasing

Hi,

In a past posting I mentioned that my oil fired hot water heater occasionally rumbled as if stone were dumped inside. Also the safety valve released water - mabe twice a week.

Well thee were several responses from a failed linner to a bad safety valve.

I tried to get someone out to look at this - all calls unanswered. It seems they only want emergency replacement jobs.

So i purchases a new drain valve and a new safety valve and drained the heater. No glass or mineral deposits. Still don't know where the noise is coming from.

I replace the safety valve and I'm still getting water out of the new safety valve.

I tried lowering the water temperature from 140 to 130 to 120 and still the safety valve releases.

Maybe the oil gun is firing to hard? Is there an adjustment for the oil pressure or ????

Thanks.

Brad White_57

Thermal expansion.

The valve in question is a T&P (temperature and pressure) valve set to open at 210F and 150 PSIG. When you set your temperature down, I have to assume that worked, that the temperature did go down. You would have had scalding water if it ran away, let's take temperature off the table for now.

That leaves pressure. Absent a gauge, you probably do not know to what pressure the system has increased. If there is a check valve in the CW supply to the city water or well water, then you would need a potable water type expansion tank installed near the heater outlet. I think your issue is thermal expansion. It is relieved every time you open the hot faucet but builds anew each time you close the faucet.

Rodney Summers

Frank

I'd suspect the water pressure is at/near its spring rate. Is there any way to check the incomming water pressure? Is there currently a valve on the water main that reduces this pressure? If you have a pressure reducing valve already installed, maybe the system has no place to thermally expand and installation of a potable expansion tank is in your future.

I'd also verify the correct temperature. Could you read off or maybe take a picture of the tag (rating) on the valve.


Robert O'Connor/NJ



edit: Brad beat me to the punch...Good Luck!

Brad White_57

Great minds, Robert

I just have a tad more free time today. It is a holiday here in MA...

Thanks-
Brad

Big Ed

Death Rattle

You have a heavy mineral build up in your tank .I call it the "Death Rattle" What you hear is the energy breaking through the heavy deposits. Since the minerals took the place of the water near the bottom of the tank it's super heating down there. It will break up the glass liner which is a layer of protection for corrosion on the steel tank. The water will seep down past the broken liner and eat away at the tank....... Once you hear the noise it seem you get 5 years and the tank will rupture... Alway are the worst moment too...

Water pressure needs to be cheaked, as the others had posted you may need a pressure reducing vale and /or a thermal expantion tank...

A

Jim_47

Water Heaters

If you have a water heater fueled by oil you have to pay particular attention to the safety valve you choose.
Most of the Electric or gas 30 or 40 gallon hot water heaters are approx 33k to 45k btu's input. But if you have a 30 - 35 gallon, oil fired hot water heater, firing at the rate of .75gph at 100psi OIL pressure, you have an input of 105k btu's. Many MANY people grab the same T&P valve for the elec/gas units and expect them to work in the oil fired units. These valves are rated 100k btu. The correct T&P valve for the oil fired hot water heaters are many times more $$ than the elec/gas T&P valve. (since I am not in the van I will use my memory, I think the Watts model of valve is the 40XL but check WATTS for sure) I have seen this problem 3 times in the last year and in each case I was the second guy in. The correct valve is much more costly but it does the job just fine.

Nick L. in Vt

valve for water heater

think it's a watt's 100xl

Jim_47

correct valve sizing

The Watts 100xl is rated at 100,000 btu

The Watts 40xl is rated at 200,000 btu


Use the 100xl on Elec and Gas 30 gallon water heaters,

Use to 40xl on 30 gallon Oil Fired hot water heaters

Frank M. Tricarico

Thanks for all the replies.

Some informtion:

Cold water in is at 43psig - no reducing valve.
Old P/T valve was a Watts 100XL.
The new replacement is the same - 100XL.
When I drained the heater there was no indication of any minerals or glass. The water was clear.
The heater is a Bradford White (M132L60F110)32 gallon, 85,000 BTU, .55/.65gph(unclear). Per BW the test pressure is 300 and working pressure is 150 psig.

It seems to me that I have a couple of choices - installing a new P/T - the 40XL or the expansion tank or both.

One other thing that I did not mention is that this house has a hot water recirc. system powered by a Taco pump. The pump stopped working and I never replaced it - just shut off the electric. The water now circulates by natural circulation. Could this have anything to do with the problem?

One more if you don't mind. Assuming there is a mineral deposit - is there a chemical that I can use to disolve the minerals and clean the heater?


Thanks again,

Larry Weingarten

How about...

... a test? Put your pressure gauge on the drain valve of the heater and make it fire. Watch the pressure and see what it does, while making sure no water is used in the house. If thermal expansion is a problem, you'll see it within fifteen minutes. If it is there, than there is some sort of check valve or similar that's preventing backflow into the cold line.

Yours, Larry

Frank M. Tricarico

All,

There is a check valve located about three feet from the cold water inlet.

I spoke with the people at Watts and they confirmed the 100 XL was the correct valve and definitely recommended an expansion tank.

Thanks for all your help.

KAG

Is the T&P off the side or the top? If off the side you need an 100XL4. 100XL6 or 8 may be to close to flue chamber.