Boiler Leaks (Supply Side)

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Old 11-20-08, 05:24 AM
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Boiler Leaks (Supply Side)

I had my A.O. Smith h/w boiler serviced yesterday for what I suspected was a failing TP valve as it was leaking.

Instead they found that the bladder had failed in the expansion tank and replaced it. Now no more leaking from the TP but instead I'm getting a leak from the 9D-M2 backflow preventer and from the boiler drain valve (packing nut seems to have loosened but tightening does not stop the leak completely). The service guy was against releasing pressure with the TP before swapping out the expansion tank and instead drained the tank from the boiler drain valve. He may have been doing something with the boiler feed valve also, but I'm not sure. Any idea if draining this way without first releasing the pressure could cause the new leaks that I'm getting?
 
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Old 11-20-08, 03:31 PM
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No... I don't think the service guy caused the problem by relieving the pressure using the drain valve.

Here's the thing ... very often when any type of valve isn't operated on a regular basis, the washers and seals tend to dry out. What you describe for the drain valve is pretty common for that type of valve. If you replace it with a ball valve type drain you will probably never have the problem again ...

Not sure about the backflow preventer ... I'm kinda mystified as to how they actually work ... there's two check valves in them, with a 'vent' between them. Sometimes that vent leaks ... I think they may have a tendency to get hung up with debris from the inside of pipes ... especially pipes that don't get much flow in them for long periods of time, like the water feed to the boiler ... then, when you have some service done that requires draining the boiler, when the system is refilled, that crud inside the pipe ends up clogging check valves, and filter screens on the inlet regulator.

I'm beginning to believe that a "Y-strainer" with a 'blow down' should be standard equipment on all boiler water feed systems... right ahead of the backflow preventer... ESPECIALLY on well water systems, and any system where there is a long pipe from the source to the boiler. I betcha that all kinda little critters could grow in a pipe like that ... very little flow, year after year, stagnant water sitting in the pipe ... so why not have a way to flush that pipe periodically ?

Bottom line is that it happens all the time ... nothing he did wrong ...
 
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Old 11-20-08, 03:49 PM
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Did the previous heating tech remember to turn the water feed valve before and/or after the 9D? If there is a low pressure sensed there, the BFP will drip.
 
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Old 11-20-08, 03:56 PM
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Originally Posted by plumbingods View Post
Did the previous heating tech remember to turn the water feed valve before and/or after the 9D? If there is a low pressure sensed there, the BFP will drip.
You mean did he "flip-up" the feed valve before he reopened the water supply?

I agree with Trooper, there should be a "Y-drain" after the shutoff and before the backfill preventer. Also, I've always tested my TP on the boiler and hot water heater once a year, just because of the stagnant water/sediment thing. Tech told me not to though because that's the best chance of getting dirt into its works. That's another reason why I wondered why he wouldn't use the TP to bring down the pressure before draining.
 
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Old 11-20-08, 05:42 PM
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I'm sorry, I meant did he re-open the ball valves or stop valves before and/or after the fill valve and BFP. Did he remember to turn them all back on. If you have everything turned back on and it is up to pressure and still dripping, you will need to try to find a rebuild kit or replace the 9D BFP

Most of us techs will not blow off a relief valve unless they are trying to sell you a new valve. And If I don't have one with me, that can get costly. Most people do not regularly blow off the RV so, it will be a problem 9 times out of 10 and then we have to explain that it was not because we touched the valve etc. It may not leak for a day or two and then you are getting a call back and the customer expects you to fix it for free. So now do you understand why any veteran heating tech does not like to use the RV.
If you told him you flush it regularly, I would give it a shot, or if I absolutely need to use the RV to relieve the pressure. Relief valves should be replaced every 5 or so years so you are sure they are in proper working condition. They are one of the biggest safety devices on your boiler and water heater. I remember the days when the plumbers would reuse the old relief valve when they would replace the water heaters to save a few bucks. Finally someone said that is not safe and now they come with all water heaters.
 
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