We have two showers in our house that have the single handle valves. The anti scald devices are turned all the way to hot, but the showers just don't get above about 100 degrees. All the sink fixtures in the house get really hot when on just hot, so I know it's the mixing function of the shower valve that is limiting the amount of hot water getting to the shower. BTW, our water heater is set to 122 degrees. My only option I can think of is to replace it with a double handle valve so we can make it as hot as we'd like. We fully accept the scald risk involved. Are there any single handle valves available that do not have the anti scald device? Or am I stuck with the double handle option?
This is relatively recent science, so it may not have influenced the installation of anti-scald devices in front of your shower valves. (honestly I thought most single-handle valves had built-in anti-scald.)
There has been a long history of people showing up at hospitals with weird bacterial infections whose source was unexplained. It was sporadic and scattershot and there wasn't much for CDC to do with that. But then suddenly there was a breakout in Flint, Michigan. The CDC went to town and traced it back to water heaters kept at 45-50C. The changes in water treatment in Flint had made the problem flare up. GOTCHA!
The traditional advice was to keep water heaters at 45-50C (113-122F) to reduce incidents of scalding injuries (burns are nasty business). However with the new data about these bacteria, they determined 60C (140F) was necessary to kill the bacteria for sure.
This, in turn, requires anti-scald valves because yeah, 60C will scald.
The anti scald devices are turned all the way to hot, but the showers just don't get above about 100 degrees.
Well like I say, you may have two anti-scald valves in series - the dedicated one, and the 1-handle shower faucet itself. You might feel the pipes between them and see which one is the problem. One might be broken. Perhaps the shower faucet is adjustable - I would consult the instructions. Or replace the kaboodle - I for one would prefer a single one in the tub faucet.
If swapping your tub faucet feels like a nightmare because of having to bust up drywall, consider carefully cutting open the necessary access space, and then installing a tasteful cabinet door there. Or a friend's valve backs up against a wall framing the the toilet stall; install a partially inset medicine cabinet there. Need access to the valve? 3 screws to remove the medicine cabinet.