According to peter :
I'm about to remodel the shower and am thinking of replacing the old valve
with a pressure balance valve. Is an anti-scald valve the same as a pressure
balance valve with a hot water limiter? Why is the limiter needed? If the
water is too hot, wouldn't it be better to lower the temperature at the hot
water heater instead of restricting the hot water at the valve?

I believe a pressure balance valve is considered to be one type of anti-scald
valve, _especially_ if the pressure balance valve has a settable limiter [ie:
screw behind bezel you can semi-permanently adjust for a max temperature setting].

Lowering the temperature at the water heater is another choice, however,
from a bacterial-incubation perspective, setting it too low isn't necessarily
a good idea.

Many plumbing codes insist on 120F maximum at faucets (ie: California,
new Canadian codes), but the recommendations for water heater temperature are
higher (ie: 140F from Center for Disease Control (CDC Atlanta) or the Canadian
Ministry of Health).

The pressure balance feature, is the main advantage you simply
can't get by fiddling with the heater thermostat - prior to it,
if we turned on anything else in the house while having a shower,
we got scalded or froze.

Now, we can run the dish washer, clothes washer, wash the car and run
our irrigation system at the same time as a shower, and the shower
temperature doesn't change _at all_. No kidding. Nobody was
more surprised at that than I.

[The volume changes somewhat, but not that much - our shower heads are
fairly low flow, so, perceived strength doesn't change much with fairly
wide pressure change.]

If you meet your max temperature requirement by downsetting your water
heater, first, you don't improve the situation with simultaneous shower
and other use.

Secondly, you run a higher risk of infection. This is not particularly
significant to the average homeowner, but, CDC indicates that
approximately 6000-20,000 cases yearly of not-specifically diagnosed
pneumonia are thought to to be Legionaires Disease where the bacteria
(Legionella) thrives in water heaters that are set above 120F, but below
140F and you inhale the bacteria in the shower.

Is there any reliability issues with these valves?

Ours has been trouble free for 10 years on a well with hard water.

Some of these valves have only one control that increases both the waterflow
and water temperature, apparently the waterflow is increased to the max very
early on and subsequent turning of the handle adjust only the ratio of hot
water. I prefer being able to adjust both the temperature and the waterflow.
But looking at the spec it's hard to tell if it allows controlling both the
temperature and water flow. How do you tell?

Single single-handle units "turn" to adjust temperature, and "pull" to adjust
volume. In practise, we always have it full on, and use an adjuster in the
shower head to vary pattern and effective volume. The push-pull mode
doesn't very good at gradually changing volume anyway.

Very handy. If you want to turn the water off temporarily without affecting
temperature setting, just push the knob in without twisting. Pull back out,
same setting.

Nicer than the units you usually see in hotels.

Moen unit of some sort. Long time ago, don't remember the model. Quite
inexpensive. $60-80CDN if I recall correctly.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.