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Can You Drain & Clean a Vinyl Pool?

For concrete pools, draining and cleaning, and perhaps acid washing or pressure washing, is a routine service, performed when stains exist, water conditions are poor, or both.

Avoid draining vinyl liner pools (and fiberglass pools as well) completely, except when absolutely necessary. Big problems can result from draining a vinyl liner pool. The most common problem is that an older liner can pull away from the walls, and shrink somewhat.

This may cause wrinkles when the liner is reset and refilled, or in cases where the liner is stiff and brittle, it may 'snap', and develop large tears or rips in the fabric. Or you may get a strong rainstorm, and a high water table will push water under the liner, 'floating' the liner in an empty, or near-empty vinyl pool.

Even worse, are unstable pool walls of advanced age; walls may collapse, or tilt inward when the outward pressure is removed. Very rare, but this can happen, too.

All good reasons to not drain a vinyl liner pool. But what if you're feeling lucky? Here are some alternatives to draining a vinyl pool, or smarter ways to drain an inground vinyl pool.

Safer Ways to Drain & Clean a Vinyl Pool

Drain it halfway and refill

refill water

If your pool is a swamp, but maybe not too far gone, one method is to drain it to within 3-6" from the shallow end floor, cleaning the walls as the water drops (so algae won't dry hard). Then refill the pool to the top, start the filter, vacuum and brush, balance the chemistry and shock heavily with chlorine. You may need a LOT of chlorine, depending on the severity of the algae. If you cannot see the shallow end floor, or even down past the first step of the entry stairs, it may take $100 in pool shock.

Use Super Shock, which is 73% concentrate, the most powerful available. You may also need to drain and refill more than once. If you have a strong well, or city water to the home, that won't be a problem, and is the cheapest and safest way to bring back a dark green vinyl pool.

Drain it fast, clean it fast, reset the liner and refill

drain water

For pools that have been neglected for years, a complete draining may be necessary to remove the sludge, dead animals, bicycles, etc. Use a trash pump, which will pass large debris without clogging, and also drain the pool in a few hours. Be sure to pump the water downhill or to a drain, so that it won't come back under the pool. You can use a pressure washer (lightly!) on the vinyl, with another person on a scrub brush. Use a small amount of degreaser like TSP or Simple Green, avoiding anything too sudsy.

Remove the drain cover, and get the suction hose in there, to get all of the gunk out that you can. When clean, replace the drain cover with a new (unstained) one, and then re-set the liner using a 5-HP shop vac or high air volume blower like our Cyclone liner vac. When you set the liner, it suctions the liner tight against the walls and floor, to help remove wrinkles before filling. Keep the vac running until the water covers the shallow end floor. If the liner is old and no longer resilient, there is a good chance it won't reset without wrinkles, or it may tear when you try to reset the liner, and fill the pool.

Super Shock & Floc pool

If possible, drain half the pool and refill first, but if draining the pool (or refilling the pool) is not possible or convenient, let's bring it back with a heavy shocking of 30 ppm or higher, and if possible, floc with Alum. The first step would be to spend a day or two cleaning the pool, vacuuming to waste, brushing and skimming, or using a leaf rake to scoop debris from the floor. Remove as much organic matter as possible, to reduce the workload for your chlorine. Using chlorine to attack leaves and twigs wastes the chemical. Lower the pH level to around 7.2, where chlorine is most potent. Depending on how green the pool is, you may need 10, 20 or even 30 lbs of granular chlorine. Pre-dissolve the shock into a bucket, 5 lbs. at a time, and pour along the edge.

Keep adding chlorine until the pool turns a cloudy blue color. Still a tinge of green? Add more chlorine! Next step is to add Aluminum Sulfate, in a granular flake form, at a rate of 3 lbs per 10,000 gallons. We don't sell Alum, but some pool stores do stock the chemical. You must be able to vacuum to waste the following day, vacuuming slowly to remove the wet toilet paper 'jelly' on the floor of the pool. More on Using Alum as a Flocculent is found here. If you can't find Alum in your local store, you can buy it online. Or skip the Alum, if you have a large and effective inground pool filter that can restore water clarity, and can wait a few days for the water to clear.

What About Above Ground Vinyl Pools?

swimming in an above ground vinyl pool

Can you drain an above ground vinyl pool? Actually the same applies, although the risk is less. Above ground vinyl pool liners can also shrink when emptied of water, and without the water pushing out on the walls, there is the possibility that the walls may begin to lean-in or possibly even collapse in some cases.

For above ground pools, follow the same advice above, be careful and be aware of what is happening as a pool is drained. Most likely nothing bad will happen, although it could, so proceed with caution, and avoid draining completely if you can.

But sometimes, draining the pool is just what the doctor ordered, or is the only thing that will allow you to correct a situation. Above ground pool filters are usually a bit small for the task of bringing back very poor water, and many will struggle.


In The Swim makes every effort to provide accurate recommendations based upon current ANSI/APSP/ICC-5 2011 (R2022) standards, but codes and regulations change, and In The Swim assumes no liability for any omissions or errors in this article or the outcome of any project. You must always exercise reasonable caution, carefully read the label on all products, follow all product directions, follow any current codes and regulations that may apply, and consult with a licensed professional if in doubt about any procedures. In The Swim assumes no legal responsibility for your reliance or interpretation of the data contained herein, and makes no representations or warranties of any kind concerning the quality, safety, or suitability of the information, whether express or implied, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose.