Yes they do help and yes they are a pain to take on and off..I have not heard good things about the discs. Have they looked at a solar reel? (see link below). Do they have a heater and are they using it? If so then the solar cover would save them heating costs and pay for itself.If they have water features or there returns are breaking the water surface they are dissipating water which causes the pool to be cooler. So the first thing is to adjust the returns or jets in the pool or reduce usage of the water features.

Here is a link that might be useful: solar reel

I will give you the same answer I did over at Poolforum.

"It sounds like it might be high flow rate noise to me as well. Most likely in the pump itself. Can you describe your equipment and plumbing? Pump size/model, plumbing sizes, lengths, numbers of runs to and from the pad, etc."

But if you don't respond to questions, then no one can help.

Here is a link that might be useful: Poolforum Post

Ignore my last post. It seems to have been posted to the wrong thread.

If the pool is a really free form, your choices are the disks, which are better than nothing, a liquid fed system which disperses when the surface is disrupted slightly but reforms, or nothing at all. If the sides are straight, using one or two covers may be your solution. The two cover solution is best for dog legged and "L" shaped pools. The single cover is best for straight sided pools, such as rectangles, Grecian, or Roman shapes.

The idea of a solar cover is not to heat a pool but rather keep the evaporation at a minimum. This is the #1 loss of heat for a pool, be it day or night.

Scott