Thread: In Floor and DHW

I know it's wrong, but wanted to have a code ready if questioned. Today I had a cabin with in floor radiant heat as well as domestic hot water combined in one unit. Unlike some installations, this had no separation at all between the two. Definitely drinking and showering with water that has been through the in floor system. We use the UMC and UPC here. The house was built in 2000, so I'm surprised it was accepted, although this could have been installed after the CO was issued.

I'm thinking that the same cross connection is present as would be with a stand alone boiler that had not back flow check valve. I looked in my UMC but didn't see anything addressing the situation. Anyone know where it would be in the UPC or UMC in case I need it?

Similar Threads:

• Checking for asbestos floor tiles not easy - Mortage 101
• Floor Covering Required?
• No slope to floor drain, 2nd story.
• wall/floor cracks
• CPSC Recall: Floor Electrical Outlets

If this helps
From the 2006 IRC

SECTION P2802
WATER HEATERS USED FOR SPACE HEATING
P2802.1 Protection of potable water. Piping and components
connected to awater heater for space heating applications shall
be suitable for use with potablewater in accordance with Chapter
29. Water heaters that will be used to supply potable water
shall not be connected to a heating system or components previously
used with nonpotable-water heating appliances.
Chemicals for boiler treatment shall not be introduced into the
water heater.

Not quite. The heater is listed for use with space heating. I'm still looking in the manufacturer's instructions, but AO Smith makes it a little hard to find online.

I did find some AO Smith installation instructions. Keeping the lines separated isn't mentioned anywhere in their instructions. They have the same piece about material being suitable for potable water (it is) and not having been used previously for non-potable (it wasn't). I may need to back track on my original thought. Anyone else have an opinion or seen it somewhere else?

Other than the pump and zone valves for the in floor, the rest of the material is pretty much the same as with a domestic hot water system.

Originally Posted by Jim Robinson

I may need to back track on my original thought. Anyone else have an opinion or seen it somewhere else?

Other than the pump and zone valves for the in floor, the rest of the material is pretty much the same as with a domestic hot water system.

As long as every last inch of tubing, control, valve, pump, and fitting are suitable for use with potable water, and haven't be used for non-potable water, what exactly is the problem?

Even then, there are some issues to look out for. Typically these systems have the water temp turned up to 160F or 180F, in which case you need a mixing valve to ensure all HW taps are fed with 120F water. You might want to ensure the proper check valves, expansion tanks, and air separation valves are in place. But at that point you're looking to ensure the system was designed properly and installed as designed, which may be a bit outside of the scope of a home inspection.

FYI: a plate heat exchanger only runs a couple hundred dollars if they want to keep the setup but separate the potable water from radiant floor heating.

I also thought about the difference between this system and a hot water circulating pump to reduce time spent waiting for hot water at remote fixtures. Basically, there isn't much difference.

Originally Posted by Corn Walker

. . . . . Typically these systems have the water temp turned up to 160F or 180F, in which case you need a mixing valve to ensure all HW taps are fed with 120F water. . . . . .

FYI: a plate heat exchanger only runs a couple hundred dollars if they want to keep the setup but separate the potable water from radiant floor heating.

Whoa hold on there. I'd say the problem is that a domestic water heater delivers water at too high of a temperature to an infloor radiant system. At 120°F a floor is very uncomfortable and causes problems with adhesives, wood flooring and some carpeting.

The real concern is that the radiant portion should have a mixing valve to limit the floor radiant temp to ~105°F.

Next the heater should be ASME listed or at least labeled for use as a heating device and the pumps MUST be all brass for use in potable water systems. However I'd let the ASME listing slide but if the pumps are not brass they won't last too long.

As long as bronze pumps are used, such as a taco 006, and all the radiant tubing and fittings are rated for potable water, there should be no problem. Temp wise , you should be looking at 105 to 115 for in floor radiant depending on style and type of flooring above it.