Air bleed into a vent pipe? (wet vent question)

[Speede541]

My question is related to a CPVC fire sprinkler system, but isn't directly related to the system operation.

I intend to install a bleed valve in the attic, at the highest point in the system. It would be very convenient for me to pipe this laterally into a lav or washer/shower vent 15 feet away, just prior to these vents penetrating the roof.

Although the fire system was designed and installed by a licensed installer, and inspected / signed off by the fire marshal, it doesn't include a way to bleed entrapped air from the high point in the system, as recommended by BlazeMaster and FlameGuard.

And of course it isn't just air -- it's air followed by spurts of water until there's a smooth and steady stream flowing.

My thought is to install a ball valve at the tippy-top of the CPVC riser, connected to gently sloping ½ copper (to encourage drain-off), into a wye that I would splice into the ductile iron vent. It would only get used when I have to refill the fire sprinker system after maintenance.

My hesitation isn't the usual "unknowingly sucking a trap dry" type of wet vent concern, but of any unforeseen problems with a non-air gapped connection of what's essentially an extension of the domestic water system directly to the DWV system. We're taking a 3-story installation in an attic, serving one or two fixtures, so there's about zero chance of a waste water backup up here. And despite this, I'm considering a second ball valve at the wye just to positively isolate the two systems.

The alternative is to run my line a bit farther, penetrate an exterior wall, and vent to the outside, but there's some ladder work, stucco drilling, and weatherizing I'd rather avoid.

 

[Bluebinky]

No a pro, but that sounds exactly like a cross connection. Preventing cross connections is the main point of the plumbing code.

I would go out through a wall, or use a short piece of hose into a 5 gallon bucket.

 

[Sponsor]

 

[Bluebinky]

One idea is to place an air gap between two valves. Just an idea - wait for one of the pro's to comment...

 

[Speede541]

No a pro, but that sounds exactly like a cross connection. Preventing cross connections is the main point of the plumbing code.

Agreed, yet due to intermittent use of this bleed function and isolation I wondering... kind of like hooking the garden hose to a "drain king" and shoving it down the waste pipe to clear a blockage. And is a fire sprinkler system even considered "domestic service" in this regard? (Yes, the fire system is isolated from the domestic supply via a check valve.)

One idea is to place an air gap between two valves. Just an idea - wait for one of the pro's to comment...

I'd prefer to avoid the air gap due to having to maintain a trap in the attic, and the potential for splashing due to the surging nature of the water mixed with air.

How about a quick disconnect and braided hose for the final 18" of my run? Normally disconnected from the vent, except when I need to use it. Seems overkill, a technicality an inspector will probably never lay eyes on. Is this a rational code-complaint solution.

(You can see I'm really resistant to dumping it through my outside wall!)

 

[Bluebinky]

I'd prefer to avoid the air gap due to having to maintain a trap in the attic, and the potential for splashing due to the surging nature of the water mixed with air.

How about a quick disconnect and braided hose for the final 18" of my run? Normally disconnected from the vent, except when I need to use it. Seems overkill, a technicality an inspector will probably never lay eyes on. Is this a rational code-complaint solution.

I was thinking that the valve after the air gap would preclude the need for a trap.

As for being to code, both solutions are subject to operator error in an area accessible to non-trained personnel, so maybe not. Hopefully, one of the pros will chime in soon...