Plastic Under Pool Liner

by Paul
(Monmouth NJ)

I'm having a pool installer come to put up a new 18x33 above ground pool. It is replacing an 18x24 that was removed. Sand roots are now in the area . I live in central NJ.

What is the best bottom for new pool. Sand only, plastic under sand, or vermiculite and sand?

Hi Paul.

I prefer sand only on my installs. I feel I can get a smoother bottom using sand than I could with vermiculite. I prefer not to use plastic as I feel if your pool ever leaks the water needs to be able to soak into the ground. Otherwise it sits between the liner and the plastic and grows algae and mold.

I do use plastic when I feel the surrounding vegetation warrants it. Nearby plants and trees will shoot roots towards a pool area very quickly and the plastic can keep them down and out of site longer than without the plastic.

I would consult with your installers and see what they prefer and why. Everyone has a preference, just check out the reasons behind it.

Here is more reading about pool bases that might help.

Pool Cove and Foam Pads

Gorilla Pad, Happy Bottom and Foam

Styrofoam For Above Ground Pool

The Best Above Ground Pool Base

Base For Above Ground Pool

Foam Pool Base

Pool Floor Pads

Pool Underlay

Pool Ground Cloth

by Carol
(Pearland TX)

I'm getting ready to setup an above ground pool, I have not been able to find a ground cloth here in town, can I use any type of heavy duty plastic??

Hi Carol.

A ground cloth for above ground pools can be just about anything, or you can build the pool without one. Most of my installations are done without because I feel the pool gets better drainage should it ever leak. I have changed many liners in pools using ground cloths where the algae growing under the liner was really bad.

There are times, however, when I really want one under the pool. This could be either a rocky soil condition as an extra precaution to keep the sand separated from the rocks. Another time would be if there was a lot of vegetation around the pool or if the yard got irrigation. If I know nearby trees will be shooting roots into the pool area in the near future, a few layers of heavy plastic under the pool can keep the roots away from the liner for a few extra years.

The cloth can be landscape plastic, pool pad, Gorilla pad, rolls of roofing material or even old carpet. It really does not make any difference what you use. Keep in mind the ground cloth does not take the place of weed and grass killer, as nut grass and some weeds will grow through the plastic and then the liner very easily.

Sand or Tarp For Pool Base

If the ground is already level, is a tarp okay to put under a 16 ft round x 48 in deep pool or should it have sand?

Hi.

It's OK to use a tarp under the sand but not in place of it. A tarp will allow all the lumps and bumps of a dirt base to show through into the base of your pool. It will cause the bottom to be lumpy and uneven and therefore hard to clean.

The sand will smooth out making the bottom of your pool easier to clean and easier on the feet for walking on. The sand can also be used in the cove area. With just a tarp you still have to have a cove for the pool to be safe. The cove can be dirt, sand or foam, but it has to be there.

It's hard to beat a smooth sand base and a properly installed liner.

If, on the other hand, you are talking about a soft side pool, then I'm sure a tarp will be just fine. If you are not happy with that you can do something different for next year.

Pool Bottom

by Cindy
(Saskatchewan)

If you are installing an 18' pool on tamped clay like soil, do you have to use sand, or can you just tarp and then use carpet felt or Styrofoam?

Hi Cindy.

Sand is just one of the many options for a liner to sit on. Styrofoam, carpet, Vermiculite and a store bought pool pad are a few others. The idea is to just use something soft under the liner. The nice thing about sand is it will cover up any uneven spots in the pool area. Sand will even cover small rocks, stones or lumps in the ground.

The drawback with some of the other base materials is that they are thin and whatever is underneath them will show through once the weight of the water is on them. Sometimes sand is used under foam, or pads, for the purpose of creating a smooth surface to lay the material on. The only problem with this is you will be making footprints in the sand while you are setting a pad over it.