This should pull water out of the system through a still-open head or the
ITV if it were only a test.
Sounds logical but it won't happen. Been there, Done (tried) that.
-Bill
----- Original Message -----
From: "Ed Vining" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, January 17, 2007 10:01 AM
Subject: Re: Dry pipe systems & trapped water
I can't speak to any other systems, but this one trips at around 45
seconds. They carry about 45 psi on the air because of a couple of false
trips, so I don't think the waterlogging is having a significant effect.
As for Todd's concern, the level of the lowest branch line is about nine
feet above the level of the DPV. When the main drain is opened for
resetting, a suction head is created on the building system piping above
the DPV level. This should pull water out of the system through a
still-open head or the ITV if it were only a test. If it were only a
test, I suppose the ITV could be closed after water flowed, then the DPV
set without draining water from the ITV line. I think then there could be
water trapped in the system. Of course the DPV line would have trapped
water, waterlog or not.
I will let the client know about this possibility. Thanks Todd.
Bill Shipman <[EMAIL PROTECTED]> wrote:
Having spent 12 years installing sprinklers, 5 years in management, and
the
last 21 years designing them, I can tell you that the type of system (in
field personell terminology) is called "waterlogged". Any time that you
have trapped water in the system the trip time GREATLY increases. I've
seen
it happen many times. In fact, everytime after correcting the trapped
section of pipe, the trip time decreased to at least half of the previous
trip time. I can't explain exactly why, but it WILL happen.
-Bill
----- Original Message -----
From: "Ed Kramer"
To:
Sent: Tuesday, January 16, 2007 8:40 PM
Subject: Dry pipe systems & trapped water
I'm working on a project where the engineer is asking for the following:
A dry valve located in the basement (below grade). The pipe leading from
the dry valve will rise up (approx 7') to just below the basement
ceiling,
turn horizontally and travel to an exterior wall. At the exterior wall it
turns down (an unknown distance, but I suspect about 2'), turns
horizontally, passes through the foundation wall, travels approx 13'
underground, then turns up into an unheated dock area.
This means there would be approx 17' of trapped 4" supply pipe downstream
of the dry valve (vertical distance = 2'). I can put a drain valve on it
in the basement, but there's no guarantee it'll get used.
Assuming this trapped section of pipe becomes full of water, how will it
affect the tripping of the dry valve? Should I be concerned about it?
(Freezing of the water in the trapped section is not an issue.)
Ed Kramer
Littleton, CO
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Ed Vining
4819 John Muir Rd
Martinez CA 94553
925-228-8792
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