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NickL
Hot water expansion tank question - cold water now hot!

I built my home in 2009, never experienced any problems with hot water , but recently checked my gas fired hot water tank expansion tank and realived it was bad, air blatter leaked and no air was left in tank. So i replaced the tank(which is located on hot water side of water heater) and now after HW is used and water heater recovers if i turn on the cold water in fauctes close to HW heater , water gets hot then returns to cold. I think i understad why, which is pressure is higher in HW tank than incoming water supply and until it lowers to the same as incomomg supply water is flowing from HW supply to faucet. So 2 questions, is my thinking correct, and what do i do to fix it?

Thanks

HandyAndyInMtAiry
Re: Hot water expansion tank question - cold water now hot!

Mich,

You seem to have the expansion tank on the wrong side. Expansion tanks are normally installed above the water heater on the cold water line before it enters the water heater; however, they can really be installed anywhere on the cold water line prior to entry into the water heater. You could remover the expansion tank. Water has flowed thru pipes for centuries before people started adding that tank. As long as you have a closed system, and a pressure reducing valve, you really do not need one.

Andrew

Handy Andy In Mt Airy NC

NickL
Re: Hot water expansion tank question - cold water now hot!

Andrew, The builder installed it on the hot water side when the house was built. But only after i replaced it, did i start to notice the problem. I'm wondering if the original tank ever worked? I thought, if you had a pressure reducing valve you needed the expansion tank because reducer valve is also a check valve so pressure can not flow back past the recuder valve. I did hear  that the tank should be on the cold side, but can you help me understand how would that fix my problem? I'm thinking if pressure is higher, water will still flow from hot side untill the pressure equals out.?

Thanks for your help

Nick

 

NickL
Re: Hot water expansion tank question - cold water now hot!

Going to move the tank to the correct side.

Is there any rules as to where i have to place expansion tank. In my situation water enters house and travels 15 ft to a couple of tees , one of which feeds the HW tank. I would be much easier to place the tank near the beginning of the 15ft run, (which is after the PRV) instead of closer to the HW tank. If i install it there , there would be splits in the cold water line before the HW tank. Will the splits have any effect on how well the expansion tank works? Currently the tank is installed on the copper riser out of the HW tank, There is not much room to mount the tank on the CW riser because of other things interfering. probably why the builder installed it on the wrong side!

HandyAndyInMtAiry
Re: Hot water expansion tank question - cold water now hot!

Nick,

I have no idea what you are referring to as a split. How can you split a pipe? Read the directions that come with the one that you have. Are you sure that you purchased one that is large enough, or not too large for your situation. Did you have enough air preassue in the tank? Extend the pipe to where you need it.

But some general rules are: It should be located in the largest pipe closest to the incoming main after a pressure reducing valve. Install an isolation valve near the expansion tank so that the tank can be serviced when needed. But not between the water heater and the expansion tank. I place them on a T and support their weight as needed.

Andrew

Handy Andy In Mt Airy NC

NickL
Re: Hot water expansion tank question - cold water now hot!

I said earlier in the note, there were TEE's. The splits I referred to were the results of the tees. meaning that the CW line was not a direct line to the HW heater. The install manual does not go into that amount of detail

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