At the end of the last year, I bought this "Pool Sentry Automatic Pool Water Leveler", since it was winter then, I did not use it. I just got it out to put it in use this week. What I found was, the Leveler either can't be turned on automatically, or if I manually pushed it to turned it on, it would not automatically turn off. Basically, it's useless.
However, I was very impressed by the customer service. After I contacted them even after so many months, they refund my money right away. So, changed my product rating from 1 star to 3 star.

I bought this about a week before a 10 day vacation. I tested it before we left and it worked well. When we got home the pool level was perfect and no leaks from the unit. I didn't turn the hose on all the way, just a bit. It doesn't matter if takes 2 hours at a low rate or 30 minutes at a high rate, it's going to fill to the desired level. Now I don't have to bother the neighbors to check my pool level while I'm gone.

This is a simple plastic constructed device that you should buy if you want to maintain the water level constant in your pool. It is a float device like the one you have in your toilet. I had no such device . I live in Houston where evaporation / water loss due to use means I constantly had to monitor the pool level , otherwise the pool recirculating pump and the cleaner (Robobot) pump may run dry and need replacing ($$$). I have replaced 4 pumps in 3 years each at $400 a time. I have left the water manual valve on 4-5 times in that time and forgotten to turn it off, resulting in a high water bill. So for $70 I am a fan of the concept.

The construction is not multi year robust, the plastic is thin and no idea on effect of constant sun (UV) but it bubbles away filling the pool to my required level. Obviously if the fill level set is above your drain level from the pool you will just lose water. It needs some gravel or stones to keep it in place.

Weaknesses : Its thin plastic. The connections are plastic. The Fill up hose I bought (Apex REM 15ft) was not that supplied, just a very cheap greed hose with thin connections. I will try it and see but do not expect it to last > 1-2 years at most. I guess made cheaply in the far east.

Day one review - more after I have had it a while. Leaks at hose connector. I worked around it by adding a brass connector with shut off, which enabled me to get a better seat. However, here the fun begins. It then leaked from the unit. I had to remove fitting from the unit, add some plumbers tape and tighten. Got it to stop leaking there, but wait, then it leaked at the actual faucet, where I had a tee connector. Replaced that, and got leaks stopped, at least for now. I do not have much time to test before I will have to depend on it, so a little bit anxious. Considered a timer, also considered a pressure regulator as recommended by one of the users. Ideal would be a safety valve that shuts off if unchecked flow is encountered - I do not know if such a thing exists. Will leave it on overnight to test. Nervous about leaving unattended for long periods.

6/1/18 - update...it leaks...a lot. Had to take it apart, wrap with teflon tape

So far so good. Easy to assemble and install.

Rain Bird HT07525PSI Drip Irrigation 25 PSI Pressure Regulator, 3/4" Female Hose Thread x 3/4" Male Hose Thread

Get one of these regulators with the leveler so you don't blow out the hose. The regulator will let the water flow full force but when the valve shuts off the water flow, the pressure is 25lb instead of 60+ lbs on your water hose.