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Thread: Draining a vinyl liner pool

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    JasonLion's Avatar
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    It is never a good idea to completely drain a vinyl lined pool unless you are replacing the liner. There are also risks with a plaster pool if you have a high water table. Draining sometimes makes getting rid of algae easier but the risk is not generally worth it.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Out of curiosity, what can results be when these types of pools are drained?
    18' round Intex using BBB

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    JasonLion's Avatar
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    When you drain a vinyl liner the liner no longer has the weight of the water holding it down and it will shrink. When you go to refill the pool it is nearly impossible to get the vinyl to stretch back out enough to go back into place. Most of the time the tension will tear the vinyl before you get very far in refilling the pool. Sometimes, when the liner is less than one year old and you have a very warm sunny day it can be gotten to stretch enough but even then it can rarely be gotten to stretch just right to go back into place at all evenly. If you have a high water table things can be even worse, shifting the ground under the liner enough to cause problems putting in a new liner.

    Plaster pools are often alright, but if you have a high water table the pool can float right out of the ground. That will tear the plumbing out, damage the coping and often the deck as well, and cause the ground under the pool to shift. When the pool settles back down it will almost never go back to where it was and will often crack or even split in two.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Interesting stuff...

    If getting a liner to stretch appropriately to re-fill is difficult, how do you get it to stretch correctly on the initial fill?
    18' round Intex using BBB

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    Chris, on initial fill it is fresh from the factory and stretchable. I can attest to what Jason is saying. I have a vinyl liner pool and had to drain it several years ago after several seasons of severe pool storing. I almost lost my liner.

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    Can you drain half of the water safely?

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    JasonLion's Avatar
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    Keeping one foot of water in the shallow end is generally sufficent to keep the liner in place, as long as that is above the water table. You need to keep the water level above the water table or the exterior water pressure can deform the liner. Typically the water table is lower than that but it is good to check if you have any doubts.

    If you are draining to replace water, ie lowering CYA levels or something similar, there is no need to allow the water level to go down at all. You can simply fill the pool at the same time you are draining it. This will require slightly more fill water for a given percentage of replacement but will go more quickly and is safer.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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