STEAM system - Blowdown pipe has slight drip

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Old 10-31-10, 12:59 PM
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STEAM system - Blowdown pipe has slight drip

Hello all,
I have a gas boiler that heats our home through steam radiators. About a week ago, I had to have the drain valve replaced as it was corroded or calcified to the point where water was coming out slowly.

The plumber also drained out the boiler for me. Since then, I've noticed the blowdown pipe has a very slight drip. I keep a bucket there for when I test it anyway, so it's being caught. When off, it's maybe 1 or 2 drips a minute. When the boiler is running, it's slightly more, but not by much.

Is this something to be worried about? I check on it almost daily as it is, and my concern is if I'm losing too much water. It's a manual water feed, so I'm checking all the time as it is.

Thanks for any advice.
 

Last edited by NJT; 10-31-10 at 02:07 PM.
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Old 10-31-10, 02:05 PM
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Ooops...

I didn't read carefully, you have a STEAM system... I thought you might be referring to the pressure relief valve... (in case you've already seen my earlier post which I've over-written here...)

I'm not a steam head, perhaps one of the guys who knows steam will be along shortly...
 
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Old 10-31-10, 06:18 PM
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No valve, on any kind of system should drip. Try and get the "plumber" who changed this valve to come back and do it correctly for free. If he balks get someone else.

If this valve has a hose thread connection you can buy a brass cap in the garden section at any hardware or home improvement store. Be sure to get the hose washer/gasket with the cap. The cap is only a stop-gap measure and the valve needs to be replaced although if the original plumber won't do the cap will hold you until next spring/summer.

If the valve has a regular female pipe thread then you can use a pipe plug with Teflon tape or paste to seal the leak but it is still only a stop-gap measure.


Wear leather gloves when removing the cap or plug for the periodic blow downs.
 
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Old 10-31-10, 07:00 PM
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Hello,
I'm sorry if I wasn't clear. The drain that was replaced is fine, I was using that as a reference because the blowdown didn't drip until after the drain valve was replaced.

I should add that aside from draining and flushing, the plumbe also replaced he glass fill tube. I'm wondering if either of these things would make the blowdown drip. Like if loose sediment could have somehow made the valve on the blowdown not fully seal.

Basically it is a valve with a pipe going out. The pipe coming from it isn't something I could cap. It's like a downward spout with no threading on the end.

The valve at the bottom of the blowdown is a ball valve, and I have no idea how big of a deal it is to replace on a gas boiler.
 
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Old 10-31-10, 07:04 PM
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Okay, I'm officially confused. Maybe if you post some pictures it will become more clear.

To post pictures you need to first upload the pictures to a photo hosting site such as photobucket.com or villagephotos.com. and then post the public URLs for the pictures (or album) here. More pictures are always better than fewer. Please have CLEAR pictures and have both close up pictures and ones from a far enough distance that we can see how the various parts are interconnected.
 
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Old 10-31-10, 07:27 PM
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I've linked a photo of the boiler.

The "1" is the ball valve that I have to use when testing the blowdown and removing water. The drain that was replaced isn't pictured as its on the back of the boiler and seems fine.

The "2" is where the water is released from the blowdown, and where the slight drip is.

I imagine I have to replace the valve at "1" to make it stop dripping.

 
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Old 10-31-10, 08:29 PM
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Clear as a piece of Steuben glass now!

That is a McDonnell-Miller model 67 low water cut off. At first I was going to state that isn't the original valve but after looking at current model pictures I find that it is indeed the current model. (The last model 67 I saw in person is probably a minimum of forty years old now.) The valve IS replaceable but the cost is over $80 plus shipping.

Here is what I would do, and in fact did many years ago. Buy a ball valve of the appropriate size, I think it is a 3/4 inch pipe thread, for the discharge piping from the LWCO. Apollo and Watts are two brands that I recommend. Install the new valve downstream of the existing valve. Now you can first open the downstream valve and then blow with the original valve. Close the original valve first and then the second valve. Cost should be less than $10 for the new valve.
 
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Old 11-02-10, 08:30 AM
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Sorry for the late reply, and thank you for the suggestion.

Before I add a valve though, should I be concerned that its on the end of the discharge pipe? Is the added stress of using a ball valve on the end of the discharge pipe bad in the long run, or do you think I'm being overly cautious?

Its also OLD and a bit rusty on the end, so I'm not sure how good of a seal it'll make.
 
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Old 11-02-10, 09:03 AM
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The discharge pipe is Schedule 40 black steel - plenty strong enough. With two pipe wrenches, remove the 45-deg el. Install the new valve between just ahead of the el. You'll need to add a short nipple between the valve and the el.

If you don't like the looks of the el, replace it. Use pipe dope on the male connections.
 
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Old 11-02-10, 04:02 PM
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Mike gave you good instructions.

As for the control being old...I assure you that with that style of handle for the blowdown valve it is not all that old, unless you consider me to be ancient.
 
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Old 11-02-10, 05:03 PM
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HA! Mike ain't no 'spring chicken' Furd! Right Mike?
 
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