Backflow preventer leaking

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Old 11-05-13, 09:09 AM
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Backflow preventer leaking

My 9DM3 backflow preventer is leaking (very slowly). I'd like to service it but my question is, will the regulator (B1156F) keep water from coming back from the heating system (does it have a check valve inside it)? My guess is no since the backflow preventer is leaking and that's before it. Sounds like to service the 9DM3 you need to drain the whole system?
 
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Old 11-05-13, 01:27 PM
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will the regulator (B1156F) keep water from coming back from the heating system (does it have a check valve inside it)?
Watts does claim that there is a 'check valve' inside.

My guess is no since the backflow preventer is leaking and that's before it.
Your domestic water is also connected to this... so that could also be leaking.

Take a look at this thread for more than you'll ever need to know about backflow preventer:

http://www.doityourself.com/forum/bo...ater-line.html
 
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Old 11-05-13, 03:30 PM
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I would replace the backflow preventer rather than "service" it. (However, Watts does, I think, sell a rebuild kit for the 9D.) If the pressure reducing valve allows a little leakage while you replace the backflow preventer, you might be able to tolerate it while you work. Otherwise, you can cut any leakage by depressurizing but not draining the system.

If, in the future, you have to depressurize and drain the system, I would take that opportunity to install a ball valve in the line between the pressure reducing valve and the boiler. That will allow you to replace the PRV, if ever necessary, without draining the system.

I assume you have a shut-off valve upstream of the backflow preventer? If you shut that valve, does the leakage from the backflow preventer stop? That will tell you whether the leakage water is coming back through the PRV or from the city water supply.
 
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Old 11-05-13, 03:51 PM
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Watts does, I think, sell a rebuild kit for the 9D
I've heard tell the same... but have never seen one... and if it can be found would be willing to bet that it's so close to the price of a new valve it would be silly to rebuild.

Make sure you flush the water lines to the boiler out real good before you install the new BFP! If you don't, you'll end up with a brand new valve leaking when the 'crud' from the pipes gets under the valve seats.

I'm on private well here so perhaps more prone to 'crud' in the lines, but any basically 'unused' line will end up with 'crud' over time. Since the only time water runs through the line from your domestic to the boiler is when you add water after servicing. That water can sit in that line for YEARS at a time.

It's a dandy place for water-borne critters to live and breed also.

Here's what I did on my last install... I'm not saying to do this... just food for thought...



What you see on the left side with the tank hanging off it is a Watts RBFF doo-hickey. That red handle valve is a multi-position valve that allows isolating various parts for service. Flip the valve around and isolate the expansion tank and open the drain to relieve pressure... change tank or charge air... another position isolates the pressure reducing valve for service.

Here's a clearer pic of the RBFF:



Then, left to right, the pressure reducing valve, Watts 9D, WYE strainer, HOSE SPIGOT for periodically flushing the line and general utility use, pipe then goes down to another shutoff valve to isolate from domestic plumbing.

Yes, I know, that plastic hose on the 9D may not be to code, but inspector turned a 'blind eye' to it...
 
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Old 11-05-13, 04:07 PM
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Watts 9D rebuild kit

I've heard tell the same... but have never seen one...
They are extant: Repair Kits for 9D Dual Check Valves with Intermediate Atmospheric Vent - Backflow Prevention - Support

I'm not promoting them. I would rather replace the whole shebang. I don't know the difference in cost between a repair kit or a new 9D, and it wouldn't affect my decision if I ever have to make it.
 
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Old 11-05-13, 04:10 PM
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If I shut the supply valve off, yes it does stop leaking. I shut it off a couple days ago to try this and the floor was dry today, I turned the valve back on and there was a spot a few hours later. I like the idea of putting a ball valve in there for easy service. I'll certainly do this sometime soon.

Not sure if this would contribute to it, but I read that 'expansion tank pressure testing' thread earlier and decided to check the pressure in my tank. I closed a bunch of valves for my heat zones and water tank loops and drained the rest (where the tank is) till the pressure needle hit 0, and what do you know I only have 3 psi in the tank (no water dripped out so I'm happy about that). Trying to find a bike pump now.
 
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Old 11-05-13, 04:11 PM
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Yeah, I've seen that too... but try finding a place to buy one!

HEY! Whattaya know!

0886010 - RK 9DM2 T 1/2 - 3/4" Repair Kit - BackflowPreventer.com

$41 ...

and:

0061952 - Watts 0061952 - 1/2" 9DM3-S Dual Check Valve

Just as expected... new one is CHEAPER than rebuild kit!

I'm all for replacing it too. Union connections, ten minutes in and out, plus however long it takes to flush the crud outta the line.
 
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Old 11-05-13, 04:15 PM
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what do you know I only have 3 psi in the tank
Yup, not surprised! I bet if you checked 10 expansion tanks that have been in service 5 years or more, that all 10 would be 5 PSI or LESS. That's how neglected they are. Techs just don't pay any attention to them at all.

Make sure to follow the steps exactly, because after you pump it up the first time, the pressure in the boiler should rise due to the water that is being forced out of the tank back into the system.
 
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Old 11-05-13, 04:52 PM
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Will do thanks.

I'm curious, what harm can come to the system with an empty expansion tank, if any?
 
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Old 11-05-13, 05:04 PM
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If I shut the supply valve off, yes it does stop leaking.
OK, buy a new 9D, shut the supply valve, and replace it. Piece of cake.

I'm curious, what harm can come to the system with an empty expansion tank, if any?
"Harm"? It won't explode or catch on fire if that is what you are thinking. But, during heat-ups, the pressure may rise above 30 psi, the relief valve will lift, your basement will fill with steam, and you/your wife will freak out.

Think about it - what is the purpose of an expansion tank?
 
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Old 11-05-13, 05:09 PM
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A while back there was a poster who described his relief valve opening with a fairly loud 'report'! I think he and his spouse both had to change undies that day! This can happen if the relief valve isn't 'exercised' regularly and the 'stopper' sticks to the seat.
 
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Old 11-05-13, 05:18 PM
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Haha well I just got done filling the tank to 12 psi. Bit of air in my pipes now though. If the spirovent doesn't take care of it in the next week maybe I'll purge the lines.

When / if I need to purge... I have a hose bib on each zone, can I just open the valve and let the water run and allow the fast fill regulator keep the system pressurized? Or do I need to isolate only the one zone at a time?
 
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Old 11-05-13, 06:24 PM
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Bit of air in my pipes now though.
This could possibly have come out of the expansion tank.

Is your tank installed such that the air valve is on the bottom? The tank is 'hanging'?

Or is it 'standing on it's head'?

If on it's head it's VERY possible that you drove air that had collected in the tank out into the system.

Also if on it's head, the fact that you didn't get water might not mean a lot.

Yes, give the SpiroVent a chance to do it's magic...
 
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Old 11-05-13, 06:47 PM
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It is hanging. When I was draining, I think I let it go a little too far cause at one point I had the valve all way open and I guess there was some vacuum cause water was 'gurgling' out.
 
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Old 11-05-13, 07:02 PM
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I guess there was some vacuum cause water was 'gurgling' out.
Yeah, 'gurgle' means it was 'gulping' air... so give the SV a chance and see what happens.
 
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Old 11-20-13, 05:56 AM
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Just thought I'd share... my parents have an oil / baseboard system and I checked the pressure in their tank and it had maybe 1 psi. A guy was coming to service the boiler, so I told my father to have him check the tank pressure. The guy checked it and said it was good. I asked my father if the guy drained any water to get it to 0 psi, and he said no. Wish I was there to let this guy know that obviously there will be pressure on the bladder if the system is pressurized.
 
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Old 11-20-13, 06:56 AM
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It's really sad the state of the industry as far as technician education goes, isn't it?
 
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