backflow device question
backflow device question
(OP)
fire sprinkler system wet with single riser.
1. only check valve installed in building is the backflow device. Legal under 2002 nfpa 13
2. The fdc connection is after the backflow device
3. so if you pressure the fdc you pressure against the backflow device.
anyone have heart ache with the set up??
are backflows designed to handle pressure 150 to 200 psi against them??? maybe 175 psi max.
1. only check valve installed in building is the backflow device. Legal under 2002 nfpa 13
2. The fdc connection is after the backflow device
3. so if you pressure the fdc you pressure against the backflow device.
anyone have heart ache with the set up??
are backflows designed to handle pressure 150 to 200 psi against them??? maybe 175 psi max.





RE: backflow device question
Not to sound sarcastic, but has there been a lot of cross contamination issues lately with backflows failing when the FDC is pressurized against the backflow preventer?
Travis Mack
MFP Design, LLC
RE: backflow device question
1. the underground comes into the building
2. first thing you hit is the osy backflow osy than feeds into the building system
3. being a wet system and the fdc on the building, the fdc pipe comes in and ties into the system after the backflow
Not to sound sarcastic, but has there been a lot of cross contamination issues lately with backflows failing when the FDC is pressurized against the backflow preventer?
no problem yet but have not had an occassion for the fdc to be pressuriezed.
just have not seen the set up before with out an alarm valve after the backflow, but meets nfpa 13
RE: backflow device question
RE: backflow device question
Now it is usually given that the feed to the fire service of the building is the same or very close to that of the domestic and that if the pumper has enough pressure boost to cause backflow into the main there are more problems - but putting the FDC downstream makes all these issues moot.
RE: backflow device question
Additionally all fittings from the underground flange and spigot to the second check valve must be cement lined. Oh, and Uni-Flanges are not permitted.... only flange and spigot pieces.
IMHO I agree with the way they do it. Not bad if everyone is forced to do it the same way (and they are).
RE: backflow device question
In my neck of the woods we typically don't require Alarm valves. So it is very usual to have the incoming water come in, split for domestic and FP, backflow on the FP line, a connection from the FDC into the FP pipe between the backflow and a riser manifold. In this scenerio the backflow would be subject to the same pressure (during FDC operation) as the system described in cdafd's post. Have not heard of any particular issues with this arrangement. When performing the system pressure test the valve is subject to 225 psi test pressure if the working pressure is @ 175. This is allowed for in the 175 psi rating the manufacturers provide.
Interesting to hear about Toledo. We (Chicago area) can go galv from the incoming flange up to the backflow, then sch 10/40 whatever from there on.