Replacing a leaking boiler feed valve

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Old 11-24-12, 07:21 AM
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Replacing a leaking boiler feed valve

I fired up my 60 yr old Arcoliner for the first time this season and found that the pressure reducer/auto-feed valve is leaking. That was bad news but the good news is the pressure relief valve works and the pressure gauge on the boiler may actually be correct since it reads 30psi when the PRV starts to release.

I have three questions --

First, I have the valve in the supply line to the boiler shut off. Is there any safety issue with leaving it off for the week or two it will take to get the new parts and install them? So I have a manual fill system now?

Second, I found this handy assembly from Taco: 334-T3 - Taco 334-T3 - Taco Dual Unit Valve (Threaded)

The specs for this unit mention a check valve -- "Built-In Check to Prevent Emptying the System if Incoming Pressure Fails" -- does this mean I don't need a separate backflow preventer?

And last, while I have the system open, I thought I would drain the expansion tank -- old style in the rafters above the boiler. Is there more to this than simply draining out whatever water is inside?

Thanks for your help, you guys have been invaluable with past problems.

Randall
 
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Old 11-24-12, 09:14 AM
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Hi Randall!

First, I have the valve in the supply line to the boiler shut off. Is there any safety issue with leaving it off for the week or two it will take to get the new parts and install them? So I have a manual fill system now?
That should not be a problem as long as you do due diligence and MONITOR THE PRESSURE! Any safety concerns would come from the boiler pressure going low, or worse, firing the boiler dry.

In theory, if a system has no leaks, there should be no water loss. Hopefully you have no small leaks in the system that will allow the pressure to drop or the system to fire dry.

The specs for this unit mention a check valve -- "Built-In Check to Prevent Emptying the System if Incoming Pressure Fails" -- does this mean I don't need a separate backflow preventer?
First, if there is an ASME rated relief valve on the boiler, you don't need (or really want) the relief valve that comes with the Taco unit.

Your system as old as it is may not have a 'proper' relief valve installed. Do you know if there is another relief valve on the system?

Something like this:


image courtesy pexsupply.com

0342671 - Watts 0342671 - M335M1, 3/4" Male Pressure Relief Valve

If not, and there is an appropriate 'tapping' on the boiler, I would recommend adding it and forgetting about the relief on the water line.

Whether or not you NEED a backflow preventer depends on your local codes. Many, if not most, jurisdictions require them these days.

If you happen to be on private well water, I would HIGHLY recommend that you install one. It is MUCH more likely you will at some point lose pressure on your domestic side than if you are on city water.

My suggestion would be to install one.

And last, while I have the system open, I thought I would drain the expansion tank -- old style in the rafters above the boiler. Is there more to this than simply draining out whatever water is inside?
Is there a valve on the pipe from the boiler to the tank? Close that if there is.

The 'trick' is to get all the water out. As water drains from the tank a 'suction' will form inside the tank. Think of the finger over the drinking straw lifted out of the drink. Stays in the straw.

You need to be certain you've gotten all the water out and that it hasn't stopped because of the vacuum formed in the tank.

A long hose coiled around the floor is sure to cause problems draining.

The shortest and largest diameter hose you have (even cut an old one down for the purpose) is best. This will allow the tank to 'gulp' air through the hose.

Leave the hose fitting slightly loose at the tank to allow air to draw in. (it won't leak water... much)

When you think it's empty, remove the hose and put a bucket under the drain. You may hear GULP GULP and more water will come out.

Worst case to break the suction would be using a small air compressor to blow some air pressure back into the tank.

BOTTOM LINE

If not already there, install an ASME rated relief valve on the BOILER.

I would rather use one of these because of the all brass construction and the screen that can be removed and cleaned:

B&G FB-38

And the 9D backflow preventer:

1/2" 9D-M3 Dual Check Valve w/ Intermediate Atmospheric Vent

(that said, this is what I used on my recent install even though the 1156 is cast iron and no screen to clean):

1/2" 9-11TM3 (Combination 1156F - 9D (Threaded)

FLUSH THE BEJEEZUS out of the water line feeding the valve before you install the new one. Many NEW valves fail because of crud in the water line clogging up the works. Hose clamp a hose onto the pipe (5/8 garden hose is a nice fit on 1/2" copper with a hose clamp, if you cut an old 5/8 hose to drain your tank, use it for flushing the water line).

Install BALL VALVES on BOTH sides of the new feed valve and backflow preventer so you don't have to drain the system next time...
 
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Old 11-24-12, 09:24 AM
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Here's a pic of my install a couple months ago, this is the 'nit-pickers' version of what I consider the ultimate water feed set up:



From left to right:

Watts RBFF (you don't need this... shown to illustrate the shutoff on the boiler side of the feed valve. This RBFF valve has a shutoff built in)

1156-9D combo

WYE STRAINER (to catch anything that flushing the line might have missed)

HOSE DRAIN (ball valve type, for FUTURE flushing purposes, and general utility use)

Not pictured on the pipe leading down, another ball valve shutoff.
 
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Old 11-24-12, 06:53 PM
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NJ Trooper,

Thanks for the quick and comprehensive reply.

Your system as old as it is may not have a 'proper' relief valve installed. Do you know if there is another relief valve on the system?
...
If not, and there is an appropriate 'tapping' on the boiler, I would recommend adding it and forgetting about the relief on the water line.
You are correct, there is no ASME rated relief valve on the boiler. There's a 3/4" outlet on the top of the boiler, and I actually have a Watts valve similar to the one in your picture, but I've been unable to get the pipe plug out. An alternate location is at the tee on the main supply for heated water, where the expansion tank is plumbed in.

Is there a valve on the pipe from the boiler to the tank? Close that if there is.
The 'trick' is to get all the water out.
Of course there's no valve. Why would the original installer have made this easy to maintain? If I disconnect the expansion tank to add the ASME relief valve, however, there will be a large hole in the tank where water can run out.

If you happen to be on private well water, I would HIGHLY recommend that you install one. It is MUCH more likely you will at some point lose pressure on your domestic side than if you are on city water.
City water. I don't know what the local codes say and I don't want to know.

I would rather use one of these because of the all brass construction and the screen that can be removed and cleaned:

B&G FB-38
The current feed valve is that B&G unit, and the PRV is B&G as well. My problem with the Bell & Gossett valves nowadays is that they're made in China (according to Grainger), while Taco and Watts are American manufacturers. If I have a choice -- and can afford it -- I will choose made in the USA.

Install BALL VALVES on BOTH sides of the new feed valve and backflow preventer so you don't have to drain the system next time...
An excellent suggestion.

My bottom line is that whenever I touch old plumbing, something breaks and a minor repair turns into a major project. Nonetheless I'll probably take your advice and try to install the Watts ASME valve and a Taco or Watts feed valve and skip the PRV on the feed line.

My other bottom line is that I plan to replace the whole boiler next summer with something a bit more efficient so I had hoped to limp through this winter without major complications. I'll get back to you on this ....

Thanks again. This has to be the best forum on the internet. Quick, helpful, knowledgeable answers. You guys don't know anything about cars do you?

Randall

For your reference, there are still some pictures on Picasa from five years back. Details may have changed, but the water piping is the same.

https://picasaweb.google.com/Randall.Sluder/Arcoliner
 
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Old 11-24-12, 07:18 PM
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Taco and Watts are American manufacturers.
Is there still such a thing?

If I have a choice -- and can afford it -- I will choose made in the USA.
Me too... usually.

I don't know what the local codes say and I don't want to know.
Can't say I blame you for that!

My other bottom line is that I plan to replace the whole boiler next summer with something a bit more efficient so I had hoped to limp through this winter without major complications.
Ya know what Randall? This being the case, I myself might not do ANYTHING... just manual fill it and keep a keen eye on the pressure gauge.

You guys don't know anything about cars do you?
I've been known to turn a wrench or two (thousand), but of course you can't ask car q's here, and I don't visit the auto forums...

======================

I just looked at your pics...

It appears that your expansion tank is using the B&G ATF valve on the bottom, and I forget the name of the fitting on the boiler, but that is a B&G also. It was a pretty good system actually, and if you don't see wide pressure swings (not that I would trust that gauge, but) I don't think I would 'mess with it'. Leave well enough alone. The bottom of that tank shows a lot of rust... I sure don't think I would go torquing anything there... yeah, leave it alone. Pray for spring.

ESPECIALLY since there's not a piece of copper pipe ! You start cranking that old steel pipe and you never know WHAT yer gonna get into!
 
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Old 11-28-12, 05:37 AM
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It doesn't take much to get me to do nothing. Maybe that's the best advice.

Any thoughts on new boilers? Weil-McLain WGO, Burnham MPO? I haven't done much looking around, or a heat loss calculation yet (I did download the SlantFin software), but in any case it would be a small unit since the house is only 1700 sq ft and one-story.

Thanks again,

Randall
 
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Old 11-28-12, 04:28 PM
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I just installed the MPO in my home. Nice boiler, EASY TO CLEAN! (my primary decision tipper... I would rather snake a 4" soil line than clean a boiler.)

The WGO is OK too...

Remember, any boiler is only as good as it's install.

1700 sq ft... offhand I'm gonna say Slant-Fin is going to tell you something around 60K BTUH.
 
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