Expansion Tanks & Home Warranty


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Old 03-24-07, 11:06 AM
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Expansion Tanks & Home Warranty

We just closed escrow on a house. Our home inspector noted that the T&P valve on the water heater had a little corrosion on the outlet. As part of negotiations, we didn't make the sellers replace it.

After using the washing machine, the T&P valve would open after the water heater refilled. I then did some homework (wish I did earlier), then bought a pressure gauge and did some testing. The town water is 110 psig. The regulator works OK and lets the water pressure down to 60 psig before it goes into the water heater. The T&P valve opens at 140 psig. So I figure everything is doing what it is supposed to do, and I will need an expansion tank.

Before doing my pressure gauge testing, I had called the home warranty company to see if the T&P valve would be covered under warranty. They mentioned that only damage due to normal wear and tear was covered. Since there was a $50 deductible, I told them that I didn't want to open a claim and that I would do some more checking first (hence the pressure gauge testing).

Would a home warranty company pick up the cost to have an expansion tank installed. I have a feeling that they would say it's a pre-existing plumbing problem. Or should the home inspector picked this up? My guess is probably not, because diagnosing the problem is more involved than just walking around the house and testing stuff.

So am I stuck paying for the tank out of pocket?
 
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Old 03-24-07, 10:24 PM
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A T&P valve opens for three reasons:
1. High Temp
2. High Pressure
3. Defective valve

Chances are, the valve is simply defective. I doubt you will see an 80 psi rise in pressure simply from the water heater (60 psi to 140 psi).
Unless you have a check valve in the supply line, you don't need an expansion tank, and is probably why you don't have one already.

I'd replace the valve first and no, a warranty isn't going to pay to have new equipment installed, and an expansion tank costs less than your deductible anyway.
 
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Old 03-24-07, 10:52 PM
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Wink

Like said just put a new T/P valve on the heater and see what you have.
Cost about $7.00
 
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Old 03-26-07, 02:07 PM
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Biking Brian says he has a water pressure reducing valve on his supply line, which will definitely act as a check valve. The thermal expansion from a water heater, operating against a bottled up plumbing system, can definitely make the T&P valve discharge every time the water heater cycles. I'd say the expansion tank is necessary.

I am in charge of the backflow prevention program in my state, and one thing we strongly caution public water suppliers not to do is use check valves or pressure reducing valves on customers' water services unless suitable means are provided for the thermal expansion caused by the hot water heater. The T&P valve was never designed to operate routinely as a pressure relief valve whenever the water heater cycles.
 
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Old 03-27-07, 11:07 AM
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Do-it-yourself... and install a potable water expansion tank. The cost would be well under $100.
 
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Old 03-27-07, 11:40 AM
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Originally Posted by Beachboy
Biking Brian says he has a water pressure reducing valve on his supply line, which will definitely act as a check valve. The thermal whenever the water heater cycles.
Suppose it depends on the valve, the one I have (a watts, probably fairly a-typical) clearly states that if the feed side exceeds the supply side by more than 10 psi, the system opens to equalize the pressure, it does not act as a check valve.
 
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Old 03-27-07, 12:46 PM
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Hmmm, maybe I could replace the pressure reducing valve instead of adding an expansion tank?
 
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Old 03-27-07, 08:12 PM
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Id go for the expansion tank first. The have just small ones to use for this .The pressure reducing valve cant let pressure back out of the home
 
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Old 05-13-07, 10:13 PM
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I finally replaced the T&P valve (it's a vacation rental and it's the off-season, as it wasn't super urgent). The water heater is designed for 150 psig, and the T&P valve is set to open at 150 psig. Now after I use a bunch of hot water, the water heater refills and it pressures up to about 140-145 psig before the burner shuts off. (The old T&P valve would open at 140 psig, even though it said 150 psig on it.) Should I still think about putting in the expansion tank?
 
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Old 05-14-07, 06:15 AM
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I would if your on a cosed system...it is actually code where i live. Closed system meaning a check valve of some sort on the supply line as stated earlier in this thread.
 
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Old 05-14-07, 06:37 AM
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I don't have a check valve, but I have a regulator, which is essentially doing the same thing.
 
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Old 05-14-07, 08:53 AM
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An expansion tank certainly doesn't hurt, and they are cheap.

As stated previously, not all regulators act as check valves. The only way you will know for sure is to install a pressure gauge on your system and monitor it. Most have a high pressure needle that records the highest system pressure as well as current pressure.
 
 

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