Is a Watts 9D Dual Check back flow preventer necessary on a residential hot water boiler?

Double D

A local inspector insisted I have one on my new installation. None of the surrounding towns require one.

kcopp

Here in New Hampshire & in Maine they are required.
Some States/ Areas require a RPZ backflow preventer. (especially if you have glycol in the system.)
Makes sense to have one.
Lots of guys install the Watts 911s which does both the fast fill feature and the backflow all in one.

Jamie Hall

That local inspector sounds a lot like me when I was one, back in the time of the dinosaurs... I always required one. Depends on your local code -- and the AHJ.

kcopp

Where is this install?

Double D

The install is in New York, not too far from Lake Erie. Thanks for the suggestion in using the Watts 911s. I would consider using that one on future installs.

HVACNUT

NYS code for at least ten years now to have a BFP on residential replacement boilers. I think it was the same year a LWCO was required.

Double D

Until now, the only component they have requested was the low water cut off.

Zman

I am curious what you are using now? The small double checks are very inexpensive and seem like a reasonable way to assure cross contamination does not occur.

Double D

@Zman The inspector recommended using the Watts 9D, that's what most are using. Do the double checks you use have atmospheric vent?

Zman

The 911 is the most common setup in my area. Caleffi 573 is also popular. For a double check to be effective it needs the atmospheric vent in case of failure.

Jamie Hall

A double check is just that -- two check valves in series, usually in the same overall body. A dual check with atmospheric vent -- like the Watts 9D -- is a bit more secure. A true reduced pressure zone backflow preventer -- like the Watts 009 -- is even more secure (dang near bullet proof). Depending on you code and AHJ, one of the three may be required. If the inspector wanted a 9D, that's what you should use. The protection it furnishes is intermediate between a dual check and an RPZ.