Expansion tank needed on hot water heater?


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Old 09-11-10, 08:03 PM
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Expansion tank needed on hot water heater?

So i'm looking to replace the current hot water heater and noticed that an expansion tank is recommended...but is it needed if there's no check valve or back flow valve on the incoming cold water pipe? currently there isn't one there (the expansion tank) but i don't want to assume that's it not needed.

while we're on this subject ever heard of having the hot water circulate the water back to the tank to keep the pipes warm?
 
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Old 09-11-10, 08:28 PM
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Old 09-11-10, 08:41 PM
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Thanks Gary...i understand the concept and why people use the expansion tank.

everywhere i read it states that you use the tank when there's a back flow or check valve in the system....do you use it (exp tank) when there isn't a black flow or a check valve in the system?
 
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Old 09-12-10, 01:12 PM
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>>>everywhere i read it states that you use the tank when there's a back flow or check valve in the system....do you use it (exp tank) when there isn't a black flow or a check valve in the system?
 
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Old 09-12-10, 02:01 PM
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If you're on a public water supply and not a private well, and there are no backflow preventers, check valves, or pressure reducing valves installed on your main water line, then generally NO, expansion tanks are not required. Any thermal expansion will "expand" backwards into the water distribution system.

As for your question regarding hot water recirculation, yes these are somewhat common in residential systems. They require a small circulating pump and a return water line. The installation cost to an existing home may be more than the convenience is worth. Proponents say it reduces waste of water down the drain while you wait for it to warm up, but you have to offset that with the cost to run and maintain the small circulating pump, and the extra cost of heat lost through the recirculation piping, even if it is well insulated.
 
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Old 09-12-10, 02:41 PM
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Originally Posted by Beachboy
If you're on a public water supply and not a private well, and there are no backflow preventers, check valves, or pressure reducing valves installed on your main water line, then generally NO, expansion tanks are not required. Any thermal expansion will "expand" backwards into the water distribution system.

As for your question regarding hot water recirculation, yes these are somewhat common in residential systems. They require a small circulating pump and a return water line. The installation cost to an existing home may be more than the convenience is worth. Proponents say it reduces waste of water down the drain while you wait for it to warm up, but you have to offset that with the cost to run and maintain the small circulating pump, and the extra cost of heat lost through the recirculation piping, even if it is well insulated.
safe to assume it would be a waste of money to put in the expansion tank? yes it goes to a main water line with no valves or back flow.

so i guess money is better spent insulating the pipes instead of creating a big mess of pipes and etc?
 
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Old 09-12-10, 03:11 PM
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Many municipal water meters have check valves installed and those that don't may be changed in the near future so installing an expansion tank is a good idea in any case.

There IS a way to have more-or-less instant hot water without a pump but it requires the water heater to be in a basement and all the supply piping from the water heater to be above the water heater and in a single line from the first to last faucet. You would need to run a return line from the last faucet back to the water heater lower connection, usually the drain. Such a system will keep the pipes hot but unless you insulate all the piping except the last few feet of return the additional cost of energy (to heat the water) will likely be excessive.
 
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Old 09-12-10, 04:19 PM
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Originally Posted by furd
Many municipal water meters have check valves installed and those that don't may be changed in the near future so installing an expansion tank is a good idea in any case.
You may want to check with your water utility. I work at the state regulatory level with backflow prevention programs, and I routinely advise our public water supplies NOT to arbitrarily install check valves at residential meter sets. We advocate proper backflow protection devices such as pressure vacuum breakers or reduced pressure zone devices at specific points, such as underground lawn sprinkers, but I highly advise the public water systems in my jurisdiction against installing single or dual check valves at meter sets, as the problems caused by thermal expansion greatly offset what limited protection they provide. We've had some water systems install double check valves, only to have to remove them after numerous customer complaints over damaged water heaters due to the thermal expansion.

Of course, other states may have differing philsophies
 
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Old 09-13-10, 03:15 PM
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Hey beachboy,


I wish more water utilities would pay attention to your comments. Installing check valves willie nilly is a nuisance.

If there a good reason for doing it, that's a different story.
 
 

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