We use these in a 7 bay Wash. We just finished replacing them all, replaced 5 about 2 weeks ago, and the other 2 in 2001. I used the Paloma PH-24-mdn's. The old one's were 25-28 years old, same model.
The only thing I ever had to change in any of these heaters were the diaphragm's, they seem to last 3-4 years and they are very simple to replace.
When this wash was purchased in 1986 it had these heaters installed, they were initially plumbed with a dole dual solenoid valve and directly to the pumps, the way it was set up was you had to starve the pump just a little to create suction to pull the soap and wax into the water stream, this created cavitation problems with the pump heads (cat 530's)., so eventually we replaced that setup with small ss holding tanks, one for each bay, I mounted them on the wall a couple inches above the height of the pumps so the water is now gravity fed and this eliminated the head wash problem.
I wouldn't hesitate to use these heaters in any car wash, they are cost effective and easy to work on, and the last a long time, plus you are only heating the water when it is needed, also if you had a problem with a heater it would only be one bay.
They are mounted on the wall directly behind the pump stands, you have to leave enough space to work on the heaters and to mount and service the tanks. Behind the pumps are the best place to install them, otherwise you would have hose running all over the place.
