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We are about to replace our water heater, and one brand we are considering recommends installing a thermal expansion tank as well. A friend who does plumbing on the side said that these have become more common in recent years.
We bought our house two years ago, and the home inspecor's report stated the water pressure was normal (55 psig), well below the 80 psig level that would need a pressure regulator (which seems to be the main reason for needing a thermal expansion tank).
So, would you install a thermal expansion tank if water pressure and pressure regulators are not an issue? We plan to buy a electric heat pump water heater, if that makes a difference.
We are about to replace our water heater, and one brand we are considering recommends installing a thermal expansion tank as well. A friend who does plumbing on the side said that these have become more common in recent years.
Your 'friend' the plumber should have stated that they are a code requirement in just about every state, county, and municipal building department.
We bought our house two years ago, and the home inspecor's report stated the water pressure was normal (55 psig), well below the 80 psig level that would need a pressure regulator (which seems to be the main reason for needing a thermal expansion tank).
I have no idea what your inspector actually stated but, what you stated makes no sense at all. Almost all homes have PRV's (Pressure Reduction Valves), they reduce the water pressure from the street (which is usually around 85-105 psi) to a more manageable 35-55psi. Which of course would be totally different from a 'thermal expansion tank'(TET).
So, would you install a thermal expansion tank if water pressure and pressure regulators are not an issue? We plan to buy a electric heat pump water heater, if that makes a difference.
TET are used to absorb the pressure expansion caused by heat in a 'closed supply system'. They also reduce or eliminate the hammering effect that can occur in supply lines. Which can cause fatigue and pipe failure.
If there are no pressure issues, then no need for such devices. The minimum and maximum pressure requirements are prescriptive so if you have inadequate or excessive pressure then you can address those conditions with devices and methodology.
Your last sentence where you say you might add an electric water heating system is on point! IF you add such a device and develop issues, then you can add a tank or other device if a pressure issue develops. I would not do so preemptively myself....just one more thing to mess with so why do so unnecessarily?
It is a code requirement in my area since 2001 or so, and if the manufacturer requires it, that typically supercedes any local code as well. They are pretty cheap and easy to install, so no real reason to avoid doing it.
A neighbor switched from well water to municipal water and kept having dripping from his temp/pressure relief valve on the hot water tank. Stuck a gauge on there, and even though the incoming pressure was below 60PSI, the combination of the anti-backflow valve and the heat from the water heater were pushing house pressures up above 100 PSI. On a municipal system, I'd say these tanks are a good ounce of protection that could prevent a lot of damage from a leaking junction.
Also another note to what already has been said, some heater manufacturers are voiding warranty if there is no expansion tank installed. I would install one, it is not that expensive..
A neighbor switched from well water to municipal water and kept having dripping from his temp/pressure relief valve on the hot water tank. Stuck a gauge on there, and even though the incoming pressure was below 60PSI, the combination of the anti-backflow valve and the heat from the water heater were pushing house pressures up above 100 PSI. On a municipal system, I'd say these tanks are a good ounce of protection that could prevent a lot of damage from a leaking junction.
FWIW, If you leave that gauge on the system for a while, you'll likely see the pressure can vary a lot. I've seen 60 psi "normal", but then it suddenly spikes to 90psi... for the cost of a tank, it's really cheap insurance, although I would suggest that in the piping leading to the tank, you have a 1/4 turn ball-valve installed.
When the expansion tank fails, you can cut-off the supply of water to it temporarily, until you can get a new one. The expansion tanks typically leak when the membrane gets old - (5-10 years or so?).
FWIW, If you leave that gauge on the system for a while, you'll likely see the pressure can vary a lot. I've seen 60 psi "normal", but then it suddenly spikes to 90psi... for the cost of a tank, it's really cheap insurance, although I would suggest that in the piping leading to the tank, you have a 1/4 turn ball-valve installed.
When the expansion tank fails, you can cut-off the supply of water to it temporarily, until you can get a new one. The expansion tanks typically leak when the membrane gets old - (5-10 years or so?).
Or... You can do Like I suggested to him. Get a 4" PVC section (pressure rated) along with a cleanout endcap and adapter to the house plumbing, and shutoff valve. Fill the section of pipe with kids rubber balls and screw on the end cap. The water in the tanks is remarkably stagnant, and rubber balls today have to be "kid safe" from toxins, so they compress and expand, and if they age, you replace them for less than five bucks.
So, in my county, thermal expansion tanks are required for new construction, but not for replacements of existing water heaters. I was wondering about their necessity because of the additional space they take up, as well as the hassle and expense of additional installation.
However, after talking to a few different plumbers and the comments on this thread, we will go ahead and install a thermal expansion tank. It is fairly inexpensive preventative maintenance, especially since we are planning to buy a water heater that carries a pretty noticeable upfront premium.
Thank you for the replies and help.
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