backflow preventer vent dripping

Jim_47

When the boiler side of the device has a higher pressure than the supply or house side pressure.
the device will allow any excess to go to the drain instead of backing up into the domestic water system.

antonio

backflow vent dripping

What causes a backflow vent to drip? High inlet pressure or boiler side pressure exceeding the inlet pressure?

Shane_2

I usually see them drip if I shut off the water main for a plumbing repair, so that would mean it was doing its job when the boiler pressure is higher than the house pressure.

Shane

antonio

Thanks guys. Thats how I though it worked, just wanted to make sure before I call my customer. He actually mentioned something about house pressure to my installer so he may have a pressure problem in the home.

[Deleted User]

a bit blowing off there

can be normal due to occasional, pressure differentials, but a drip-type leak there is indicative of a leaking disc and piston assembly/o-ring/seat etc, and they're easily rebuildable
i certify and/or rebuild them

Dave Yates (GrandPAH)_2

Antonio

RPZ's spit or drip when the inlet pressure drops below the outlet pressure. Not an uncommon occurance as fixtures are used or water main pressure drops in the street and an interior draw occurs allowing the lower street pressure to be seen by the RPZ PRV. The best way we've found to eliminate that issue, is the installation of a soft-seated check valve on the inlet side of the PRV, which traps the highest inlet pressure to maintain the pressure differential required for spit-less RPZ operation.

Tilmon_2

To remedy a driping vent on a backflow preventer I begin by cleaning it, if that doen't work I install a check valve upstream, and if that doesn't work replace it. ( this is for residential type "watts 9D" backflow preventer)

[Deleted User]

drip or spit?

Watts Trouble Shooting Guide - Backflow Preventers
Problem Cause Solution

for a spit, watts says;

A. Valve spits periodically from the vent.
A.1 Fluctuating supply pressure.
A.2 Fluctuating downstream pressure.

A.1 Install a soft seated check valve immediately
upstream of the device. (Watts 3⁄4" - 2" No. 601
bronze valve.)
A.2 Install a soft seated check valve downstream of
the device close as possible to the shutoff valve.
(Watts 3⁄4" - 2" No. 601 bronze valve.)

for a drip, watts says;

B. Valve drips continually from the vent
B.1 Fouled first check.
B.2 Damaged or fouled relief valve seat.
B.3 Relief valve piston o-ring not free to move
due to pipe scale, dirt or build up of
mineral deposits.
B.4 Excessive back pressure, freezing or water
hammer has distorted the second check.
B.5 Electrolysis of relief valve seat or first
check seats.
B.6 Valve improperly reassembled.

B.1 Flush valve. If flushing does not resolve problem,
disassemble valve and clean or replace the
first check.
B.2 Clean or replace the relief valve seat.
B.3 Clean, grease or replace the piston o-ring.
B.4 Eliminate source of excessive back pressure or
water hammer in the system downstream of the
device. Use Watts No. 601 to dampen out back
pressure and No. 15 to eliminate water hammer.
Replace defective second check assembly. In
case of freezing; thaw, disassemble and inspect
internal components. Replace as necessary.
B.5 Replace relief valve seat or inlet cover. Install
dielectric unions (Watts series 3001 through 3006).
Electrically ground the piping system and/or electrically
isolate the device with plastic pipe immediately
upstream and downstream of the device.
B.6 If valve is disassembled during installation, caution
must be exercised to install check springs in their
proper location.

mtfallsmikey

Did you

go ahead and rebuild the RPZ?...always a good idea..get the relief, 1st and 2nd checks..also test (and record the results!)

Al Corelli_2

Backflow Drip

We do what Tilman does. Each install gets a swing check before ANY backflow device.

Really keeps those "my new boiler is leaking" calls from happening.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Unknown

Eliminate the problem altogether

After so many jobs with leaking 9Ds , we switched to a ventless backflow preventer for our residential installs .

Is a vented backflow a requirement in most places ? If so , why ?

[Deleted User]

IPC 608.16.2

connection to boilers sez;
The potable supply to the boiler shall be equipped with a backflow preventer with an intermediate atmospheric vent complying with ASSE 1012 or CSA B64.3. Where conditioning chemicals are introduced into the system, the potable water connection shall be protected by an air gap or a reduced pressure principle backflow preventer, complying with ASSE 1013, CSA B64.4 or AWWA C511.

why vented?
in the event of failure for whatever reason, the water can be safely discharged

Unknown

Thanks Mike

for the excerpt .

Although the vented backflow seems like overkill if you have that and a PRV on the makeup water pipe . Just thinking about what would have to happen ........ the pressure on the house side would have to be very low or nil , and the PRV and the ventless backflow would both have to fail and let water flow in the wrong direction ..... at the same time .

[Deleted User]

my pleasure

and part of the concern is where, under the right conditions, boiler chemicals can be 'pulled' back into the city main, and potentially contaminate the neighborhood etc

and if you can locate, or maybe download them, check out the spooky stories in the EPA's cross-contamination control manual, and/or the watts regulator's pamphlet.
and in these litigious days............

nicholas bonham-carter

backflow substitute

i stiil think my own [pre backflow regulations] arrangement is best and simplest [never needs a yearly $75.00 "tuneup"]--a spring-loaded shower valve for the makeup feed line into my one pipe boiler.
i would think that most systems with an appropriately sized reserve tank could be filled with a hose [maybe from the hot water heater]once a season thus doing away from the necessity of having to have it serviced so frequently.
speaking of epa horror stories have you ever had any experience yourselves? the HO is far more likely to be drinking water backing out of his sprinkler system than from his boiler
i might add that of course i do have a backflow on my boiler, i just hate being required to install a seemingly unnecessary $500.00 item just because "mommy says".
--nbc

[Deleted User]

amen to the

filling it with a garden hose. i do the same meself. inconvenient but......

hey, is your sis in sweeney?

mtfallsmikey

My fav cross-connection story

Someone adding water to a 55 gal. drum with Chlordane in Roanoke Va....no backflow preventer on the hose bibb, lost pressure, ALL of it got sucked back into the main...city had to replace about 1 mile of main...was the opening of the cross-connection certification class I did in '95.

[Deleted User]

yearly certs

have become the norm, and law in some states, for many high risk environments

something as innocuous as the fire dept flushing hydrants, can cause enough of a pressure drop, which can pull water from a near-by bldg's treated boiler or similar vessel, into the local supply water. firefighters leave, cooties stay in the supply system for the locals to drink