Time for a rant.

Over half of times I stay in a hotel, apartment, condo or whatever, whereever, there are always issues with water temperature.

Sometimes also with water pressure, but the temperature issues are more annoying since the temp will often vary between very hot and quite cold.

Many places have these small individual electric-powered heaters, sometimes even made in Germany, but they don't seem able to maintain a constant temperature.

Why is that and why aren't those little +%$"%$& working correctly?

Only one solution: upgrade your choice of accommodation

They're probably the same type of water heaters that we have in our upstairs bathroom. There's three settings -- off, medium, maximum, and there doesn't seem to be a thermostat in it. Instead of judging the current temperature of the water, it simply heats up the heating rods to a specific temperature. So if it's a cold day, the water is perfect on medium, but if it's a hot day, the water is almost boiling on medium.

If you ever have to install one of these individual electric shower heaters, you'll see (on the installation instructions), that the water supplied to the inlet should be at a certain pressure. If you happen to shower at a time of high water demand in your hotel/condo/apartment block, that pressure may be reduced and that has an effect. Also, by opening or reducing the supply tap (that's in your control), you'll get cooler water on high flow than you will on low flow, assuming your temperature control adjustment remains constant. Got it?

Next, the ambient water temperature has much to do with it. During the hot months we don't even turn on our shower heater - and the water comes through well hot. Come the cold season, we might have that sucker turned up to the max and still have to reduce the water flow to get warm water. The larger capacity water heaters tend to work more reliably I think.

Actually the problems go away when you have water supplied at a constant pressure and a constant ambient temperature, but when has anything ever been reliably constant in this non-utopian world? Taking cold water scoop baths in an Issan bathroom in December focuses the mind most wonderfully, I recall, and the installation of our first hot water shower was reason enough for a party!

Same problem in hotels all over the world, not specific to Thailand

If you ever have to install one of these individual electric shower heaters, you'll see (on the installation instructions), that the water supplied to the inlet should be at a certain pressure. If you happen to shower at a time of high water demand in your hotel/condo/apartment block, that pressure may be reduced and that has an effect. Also, by opening or reducing the supply tap (that's in your control), you'll get cooler water on high flow than you will on low flow, assuming your temperature control adjustment remains constant. Got it?

Next, the ambient water temperature has much to do with it. During the hot months we don't even turn on our shower heater - and the water comes through well hot. Come the cold season, we might have that sucker turned up to the max and still have to reduce the water flow to get warm water. The larger capacity water heaters tend to work more reliably I think.

Actually the problems go away when you have water supplied at a constant pressure and a constant ambient temperature, but when has anything ever been reliably constant in this non-utopian world? Taking cold water scoop baths in an Issan bathroom in December focuses the mind most wonderfully, I recall, and the installation of our first hot water shower was reason enough for a party!

+1

Yeah, that would be a great concern this time a year {and more than two-thirds of any given year} - whether my shower water was hot enough when it's 38-40 degrees every bladdy day. Being the curious sort that I am, I'd first wonder what the hell is wrong with these sorts.

There are two types of individual water heaters, electric ones, and the ones running on gas. When travelling in northern Thailand in 1999, I noticed up there they were using a lot of the gas operated ones, does this still apply?