Pool Cover Water Tubes and Air Pillows

What does the air pillow actually do?

It takes the ice expansion. Freezing water needs more room than liquid water, and in a pool with no soft spot anywhere in it, the only direction left is sideways into the walls. Float a pillow under the cover and the ice closes on that instead, squashing something that is meant to squash. Most people buy one thinking the job is holding the cover clear of the water so rain runs to the edges. That happens, and it is useful, but it is the side effect rather than the reason the part exists.

Is a water bag the same as a water tube?

Yes. Two names for the same thing, and you will see both on the same shelf. They are vinyl tubes you fill on site from a hose and lay end to end around the edge of the cover, and they are the standard way of holding an inground winter cover down. An above ground pool does not use them at all: that cover is held by a steel cable through the grommets and a winch that pulls it tight.

Single chamber or double?

Double, if you are choosing. The dual version puts two independent bladders inside one sleeve, so a puncture at one end drains half the weight and leaves the rest sitting where you put it. A single compartment tube that goes loses all its weight at once and leaves a gap in the ring at exactly the point the wind gets under the cover. The price difference is a few dollars a tube and you are buying fifteen or twenty of them.

What does the gauge mean, and is higher better?

Higher is thicker, which is the opposite of wire gauge and catches people out. We stock three grades, and the heaviest of them is the 30, with the 20 in the middle and the 16 as the thin one. The honest caveat: on vinyl, gauge is a number the maker chooses rather than something measured, so it ranks one brand's own tubes reliably and tells you very little when you set two different brands side by side. Mil is the measured figure, and nobody sells tubes in it.

What size air pillow do I need?

It is sized to the pool, not to the cover, and bigger is the safer error. A small round above ground pool takes the 4 by 4 ft; the larger rounds and ovals take a 4 by 8 ft; the biggest ovals and rectangles take the 4.5 by 15 ft. The pillow has to sit roughly in the middle with room for the ice to close in on it from every side, so one that is too small for the pool gives the ice less to push into and does less of the job it was bought for.

Can I reuse the tubes and the pillow next year?

Tubes usually, pillows often not. Drain the tubes completely before you store them, because water left in one freezes in the garage and splits it in the place you will not find until October. Dry them, fold them loosely and keep them out of the sun. A pillow that has spent a winter under ice has usually been punctured or has gone soft at the seams, so plan on it being a yearly part and be pleased when it is not.