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Thread: Expansion tanks

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  1. #1
    DIY Member mariner's Avatar
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    Default Expansion tanks

    Hi,

    Please bear with me on this as I am not quite clear about the expansion tank issue.

    First, my water supply is from a well, it comes into the house through a check valve and then into a pressure tank at a tee in the line. The water also goes through filter and softener and then to the house via the hot and cold lines. There is no other expansion tank fitted anywhere.

    I find there is a noticeable change in pressure when in the shower, when water is turned on somewhere else in the house.

    I am thinking of putting in an expansion tank to hopefully level off the pressure changes when the shower is being used and water is used elsewhere. The extra "cushion" if you like, would hopefully reduce pressure changes.

    Would an expansion tank work ok with the connection at the bottom - with the tank verticle. Would the tank do it's intended work if above the floor boards but below sink level. I ask this as I am pushed for suitable space under the floor but could use a small closet to put the expansion tank in.

    I don't know if this makes any sense - I hope it does.

    Thanks for any and all input.

    mariner

    http://www.watts.com/pdf/1915356.pdf
    Last edited by Terry; 10-27-2008 at 11:29 AM.

  2. #2
    Master Plumber nhmaster's Avatar
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    An expansion tank will not solve your problem nor will it have any effect at all. What you have is inadequatly sized piping causing your problem.

  3. #3
    In the Trades Gary Swart's Avatar
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    As nhmaster points out, an expansion tank will not solve your problem. A thermal expansion tank is used to absorb the expansion caused by a water heater when the system is closed. It does not equalize pressure in the system. When there is a closed system without an expansion tank, when the water heats, pressure will rise in the heater resulting in the T/P valve tripping.

  4. #4
    Like an engineer alternety's Avatar
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    Do you check you filter regularly. If it is clogged it will cause what you are talking about. If the resin bed in the softener clogs, same problem.

    If either of these two devices are undersized they could cause excessive pressure drop. Was it always like this or is it something that has developed over time? If always, it is probably a design issue somewhere. If it developed, a clog or deposits inside pipes.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    Assuming you have a typical well pump system (for the USA anyways), your pressure tank for the house would perform the same function as one used with a WH and a PRV.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    DIY Member mariner's Avatar
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    Default Expansion tanks

    Hi Guys,

    Thanks for the comments thus far. The inlet piping is going to be increased in size - that was already on the books. What I was interested in is using another expansion tank ($40) making two in the system, as opposed to putting a larger pressure tank ($$$'s)in the system - to achieve some cushioning or pressure damping if you like. The pressure variation/difference isn't a lot, but can be felt. The present pressure tank is 33galls (Well Rite WR120R) and I suspect a larger size would accomplish two things - reduce number of pump starts and allow better pressure delivery. The expansion tank I was looking at is around 15" dia and about 20" long (my guess) and would help to achive less starts and better fluctuations.

    If my reasoning is wrong please let me know.

    I know installing expansion tanks in rv's does reduce pump starts and evens out pressure variation better. Carrying this across to the house/home says similar improvements should be accomplished.

    Thx

    mariner

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