Can You Drain & Clean a Vinyl Pool?

drain and clean 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.

6 thoughts on “Can You Drain & Clean a Vinyl Pool?

  1. I have a above ground round pool that is 30ft. I had issues with moles going underneath the pool and causing holes underneath the liner. I wanted to drain it and try and fill in these holes so the liner doesn’t bust. Is it a good idea to do or should I leave it?

    • Hi Rachel, I understand, how horrible. Yes, you will need to do this, and there’s no issues – it’s just like a liner replacement, and if needed, could be done at the same time, or if the liner is in good shape, just reset it. Just have to be careful in removing the liner, and folding and storing very carefully, while pool floor is filled in and smoothed. Unless you have an ‘overlap’ liner, be careful not to raise the floor, or make the pool more shallow, then the liner can wrinkle. Then just replace the liner, and replace the wall fittings / faceplates (tightly), and refill with water, working out any floor wrinkles, pushing them to the edges. Balance the water and start filtering. Then most importantly, install some sort of mole repellent, around the pool, do those sonic spikes work? Or a ring of some chemical or substance that would cause them to turn back…

  2. Rita Ellison

    My above ground pool is green after adding maratic acid. Please help

    • Hi Rita, probably not the cause of the green, more likely low chlorine level and/or not enough filtration. However, if it is a very CLEAR, BRIGHT green color, it could be metals, knocked out of solution by the chemistry change. In such case, add a Stain & Scale chemical like MetalFree or our Stain Away, to redissolve the metals. If dull, cloudy green however, it would surely be algae.

      • George Richardson

        Hello ,around ten years ago we had a liner installed in our gunite inground pool with vermiculite based floor .We had pool foam laid under the liner in the shallow because our father had Rheumatoid Arthritis .We never had a problem with it and it was soft on the feet .Now we are having a new liner put in and are being told that we shoud not use a pad on the floor under the liner . What do you say ? Thank you

        • They probably say that because the joints where the pad intersects will be visible under the liner, and if the pad sections are not completely flush and even, there could be a thin joint that can trap dirt, and grow algae. Also in the case of sloped floors, it is possible that some pad may slip and bunch-up, creating lumps or liner wrinkles, making liner damage in that area a possibility. However, if it worked fine for you before, and the same pad can still be purchased (was it “Happy Pad”?) then go for it! It might make sense to glue it to the floor with 3M spray adhesive, so it won’t shift.

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