Thermal Expansion

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Anon125

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a few months ago we replaced our gas water heater.
the 'overflow' pipe often has water dripping out and it sometimes splashes on the floor.
i thought we just needed a longer hosepipe.

but we twice phoned RHEEM.
first reply "that is normal"

second reply ' you need a thermal expansion tank"

not keen on spending yet more money on it....

suggestions welcome.
we got it from home depot.

thanks all
 

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Reach4

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second reply ' you need a thermal expansion tank"
Right answer.

To prove it to yourself, you can get a pressure gauge.

Find a thermal expansion tank calculator or table to make sure you get a big-enough one.

There is an alternative to have a device release your expanded city water to a drain at maybe 100 PSI or so. That takes a little extra water, of course, so not good for water shortages.
 

Reach4

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Thanks, the water just drips out.
It does that after you have been using hot water, such as during a shower, and then you stop using water.

Presumably if you are using water, even a tiny trickle, the dripping stops. If not, then there is a different problem.
 

Anon125

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so the dripping is normal?
will a longer hose so that it is nearer to the drain hole be a good idea?
It would stop it splashing to the floor!
thanks
 

Reach4

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so the dripping is normal?

If your water pressure rises to 150 PSI, it is normal and important for that to drip. If you have a closed system with no thermal expansion tank, it is expected that the water pressure will go to 150 PSI.

But if your water pressure goes to 150 PSI, it is important for that to drip. It is not normal that you would just let that happen over and over.

Adding a hose is not a good idea. You want to know when it happens, because it is not normal to have your water pressure at 150 PSI.

It should not happen. Is it normal? It depends on how you define normal. Normal is to have an a working expansion tank if you have a closed water system (one-way valve on the incoming water).

Is it proper for the T+P to drip if you have a "closed system" and no working expansion tank. Yes. Did they replace your water meter or did you have other plumbing work done? During that work, your plumbing could have been converted to a closed system.

Get a pressure gauge if you want to know what is going on. That is easy and cheap. Some have a second "lazy" or "tattletale" hand to remember the peak pressure.
 
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Anon125

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what are all these things on top of the tank?
the 3rd rheem guy though the water pressure was too high. this tank can 60PSI
thanks guys

PS water company says our OUTSIDE water pressure is about 75psi

one of those things looks like a (one-way valve on the incoming water).

would not know where to use the pressure guage!
 

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Jadnashua

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Since water doesn't really compress under pressure, and copper pipes are pretty rigid, any heating of that water will cause it to expand and instantly raise the pressure. The parts that might help contain that are the supply hoses to faucets, washing machines, toilets, etc. that can start to balloon (stressing them and shortening their lives in the process). But those are all designed for domestic water pressure, and that is limited to 80psi or lower. The T&P valve is designed to open above 150psi (or 210-degrees). You risk blowing out a weak hose, as well as causing a seal to leak on any valve. If all of the valves and hoses are in good working condition, the pressure will spike almost instantly while heating and you stop using any water anywhere (any small leak can relieve the pressure). Ideally, especially since the T&P valve on the WH is designed for emergency use, you'd prevent it from opening on a regular basis which could cause it to either never close or not open and allow things to get way out of hand. So, if you have a properly sized and installed expansion tank in your system, the bladder in that tank can compress the air on the other side, allowing the water to expand and if the thing is sized properly, the pressure will barely register as rising at all. Once you open a faucet, the water that is pushed into that tank will come out, putting the bladder back at its neutral position, ready for the next cycle. They do wear out, they do need to be eventually replaced, but they can last a significant number of years and they're not expensive.
 

Anon125

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when the home depot installed the water heater last year they did not mention an expansion tank. probably because the 13 year old one worked fine without it.
thanks
 

Jadnashua

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Unless you have what is called a closed system (PRV, check valve, etc.), you often don't 'need' an expansion tank. But, many utility companies and code areas are working together to require an ET to account for the progressive installation of check valves in the supply system used to help prevent any backflow that could pollute the main system. Without a closed system, that water that expands has a path - back out to the supply side...close that off, and you need someplace for that expanded water to go, and that's best done with an ET.

For a number of years where I live, assuming you got a permit to change your WH, they've required both an ET and a tempering valve. This is fairly common in many places. It means that you won't have issues when the utility eventually updates their meters and supply system which almost always includes a check valve.
 

Gary Swart

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This is a classic case of the need for an expansion tank. I learned this several years ago when I installed a PRV. Suddenly my TP was leaking water. I changed TP and still had the leak. I explored the problem on this forum and learned. Got a pressure gauge and tested. It was amazing to see how fast the pressure zoomed up from 50 PSI to 150 PSI! Got the expansion tank, installed it, and no more TP leak. If you were getting by with the TP leak before the new tank, it's possible there was a weak flush valve in a toilet that would release the expansion without being noticed.
 

Treeman

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I hope you guys are still watching this thread. I've lived in our house for over 35 years. It is supplied by a well and the water heater(s) have been fine WITHOUT any expansion tank. I understand that ours is an OPEN system and water can expand backwards towards the well.

At least one article states that a water softener can act as a check valve, creating a closed system. We have a water softener where the water comes into the basement. I just replaced the 20 + year old unit with a new Clack WS1 valved unit. A professional plumber did the install.

Do I need an expansion tank?? Thank you.
 

Reach4

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I hope you guys are still watching this thread. I've lived in our house for over 35 years. It is supplied by a well and the water heater(s) have been fine WITHOUT any expansion tank. I understand that ours is an OPEN system and water can expand backwards towards the well.
The water expands into your pressure tank, which is like a thermal expansion tank, but it is much bigger.
 

Treeman

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The water expands into your pressure tank, which is like a thermal expansion tank, but it is much bigger.

I apologize. I am on a public well system (of sorts). There is no meter and the backflow preventer is at the well house about 800 feet away. We just have a one inch plastic line coming into the basement (no pressure tank). The one inch line connects off a 3 or 4 inch line that also serves other buildings.

Again, does the water softener act to create a closed system (check valve), as some sites claim?

Thanks!
 

Reach4

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Again, does the water softener act to create a closed system (check valve), as some sites claim?
No. It may be that a softener could close off the water for a brief period during a regeneration, and that a power failure at a fairly precise time couldn't block things for a longer period, but that is unlikely.

That does not mean there is not a check valve in your system. If that were the case, your T+P valve would have dribbled in the past.

There are pressure gauges, with a garden hose thread, that can record peak pressure with a second "lazy"/"tattletale" hand. The Watts DP IWTG is one. These can be inexpensive. If things do show high, note that these can be affected by vibration or pulses. A high recorded reading would indicate you might look further.
 
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