This is a great invention for monitoring indoor pools and hot tubs. Just stick one in the skimmer of each pool, tie it to the skimmer basket and screw down the lid so children can't fish it out and you have a constant temp reading on the wall for both the pool and hot tubs. With two units you can monitor both pool and hot tub on each wall unit. Each wall unit has the capability of actually monitoring three units and it also reads the current air temperature which is nice for an indoor pool. It doesn't read humidity but that would be a nice additional feature. They are accurate and save the time of constantly measuring the water temp. The 102 degree hot tub temp doesn't seem to harm them at all. What a fantastic idea for both indoor pool use all year long and outdoor pool use in summer. So why are they so cheap?
Here's the problem. The tie down is no more than a piece of string- you need nylon cord to secure it. Not a deal breaker. It doesn't float upright because there is not enough weight on the bottom stem. It lays on its side which means the cover gasket is always partly under water. It slowly builds up moisture inside the sealed unit until it quits sending a signal. Either the batteries fail or it shorts out the circuit board. You have to remove 5 screws and the gasket to dry and reset the unit from inside whenever it quits working. I thought at first it was just condensation inside but it is not. Opening it up causes the seal to be even less secure and the gasket will start to deform making it harder to seal properly. The clear plastic cover is prone to small cracks as well when tightening the screws which adds to the moisture problem. There is no way to initiate it or reset it from outside without compromising the seal from first use. I have purchased 5 units over the last year for two hotels with a hot tub and pool each. I liked them so well at the first hotel that I bought two more for the other hotel before the first one quit. After messing with them for nearly a year I found that by drying them out and cleaning any chemical residue inside and swapping parts around, I can usually keep each one going for a few months before the next problem. Silicone o-ring lube helps seal the gasket and marine goop helps seal the small cracks in the cover but weights applied to the bottom stem to keep them upright just rust or come off. The batteries in the lower stem are just not heavy enough to offset the top heavy upper part. It simply needs a heavier stem to float correctly.
They have made one change internally from my first units to the later units by fixing an internal connector that was prone to come loose. They used to put a note inside to remind you to make sure it is tight before sealing the unit. If it comes loose from bouncing around it quits and you have to open the unit again to fix it. Now they attach that plug permanently and use a clip connector to separate the wire between the upper and the lower parts of the floater unit. That solves one problem but not the major flaw. They need to add weight to the bottom to it floats upright and raise the top so that the sealing gasket between the top and bottom is way above the water level. That and a stronger clear top that won't crack and maybe they would finally have a design that lasts. A nylon cord and a hook to secure it would be a nice touch as well. If they get this improved, every commercial pool and spa in the country would pay three times as much for these units. As on now consider it a cheap throw away and buy several so you can dry them and rotate parts or just go back to the old fashioned thermometer on a string. Someone will eventually make a much better unit and probably make a lot of money.