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Drain boiler to replace boiler drain?

The 1/4 turn boiler drain on my boiler is leaking from the stem.  Nothing to tighten or replace, seems the ball and stem is totally sealed in the two halves of the casting.

On the attached sketch,  the lower boiler drain is leaking.  I can isolate the boiler itself by shutting the two gate valves.   I am concerned about cracking the boiler if I drain out the water and then refill with cold water.  I probably can rig up feeding the boiler from the hot water tank.

What I am hoping is, if I remove the lower boiler drain (after relieving the pressure),  will the water will stay in the boiler (i.e. finger over the soda straw),  since all the gate valves are closed?  Will that work?  It is 3/4" thread into the lower boiler.


  • ZmanZman Member Posts: 3,561

    Is there some reason the boiler has to be hot?

    Why not turn it off for a couple hours. then isolate and drain the boiler. You could try to leave the water in, why bother. You will get a better seal if the fitting is clean and dry.

    You will not crack the boiler putting cold water in a boiler that is less than 120 degrees or so.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Patchogue PhilPatchogue Phil Member Posts: 265
    edited January 2014
    Keepin boiler hot

    "Is there some reason the boiler has to be hot?

    Why not turn it off for a couple hours. then isolate and drain the boiler."

    Yeah!  :-) 
  • Patchogue PhilPatchogue Phil Member Posts: 265

    I just don't want to tempt fate with a 20 yr old steel boiler when we are getting a foot of snow tomorrow during these "Artic Blast" low temps upon my area.
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,579
    Leak cure

    Can you put a cap on the output threads until the spring?--NBC
  • unclejohnunclejohn Member Posts: 931

    It's pouring out the stem just wait unitill the cold weather passes. But you wont crack the boiler by draining it, swaping out the BD and then you can let system water back into the boiler and bleed the rads.
  • M LaneM Lane Member Posts: 123

    Don't use a Mueller (Home Depot) again when you do this. When you say leaking from the stem, the water is coming out from under the handle? If its only dripping out of the nozzle use a brass hose thread cap.
  • Patchogue PhilPatchogue Phil Member Posts: 265
    Stem leak

    Definitely leaking out from around the stem.
  • icesailoricesailor Member Posts: 7,265


    I think you know your way around a boiler. Turn the high limit down as low as you can get it and turn up the thermostat. When the burner finally comes on, shut off the power. The boiler is now cold.

    Close the gate valves to the system. Lucky you, I'm never that lucky. If you have a boiler drain at the top like in your drawing, LEAVE IT CLOSED. If there are any float vents with caps, tighten them DOWN.

    Take a big pair of pliers or the tool of your choice. Start to turn it lose but stop. Take a new drain of your choice, preferably one with a packing nut and NOT an O-Ring, and prepare it for use. I prefer to use Teflon Tape and paste on the male threads. Take a 5 gallon bucket and a short piece of hose (Washing Machine hosed are my hose of choice) and drain water into the bucket. After the water stops (very shortly unless you have a Extrol in which case it will run a little longer. Have two buckets if you're chicken. I've never needed more than one. Have the new drain ready, unscrew the old one, and pop the new one back in its place. You can have a container under the fitting but the most I ever get might be two cups of water. Put the thing back in service.

    I've done it for years. Let old Mother Nature help you out.

    I routinely changed bottom elements on electric water heaters by replacing the vacuum valve with a plug, beating the edge of the element flange with a big old beater screwdriver, and when it moved, I had the new element greased up and ready to go. I'd pull out the old one and slam the new one in its place. I never lost more than a quart of water. (after relieving the pressure on the tank of course.).

    Don't worry about the temperature of the water going into the boiler. I've started up boilers that had been off in frozen houses and when the circulators came on, the water was so cold, you couldn't hold your hand on it. It never cracked any boiler I ever saw.

    The only one I ever saw cracked was one that was off in a drained house and cleaners went there to clean. Someone turned on the water but not the heat. The girls were cold and had no hot water. So, they turned on the switch. The boiler ran fine. The hot water didn't get hot and the house stayed cold. When I got there, I saw the first Weil-McLain 568 series boiler partially painted red with the factory blue still on it. I shut it off and went back the next day. The red was unpainted metal gray. The boiler leaked. I replaced it.

    Live life on the edge. Change it on the fly.
  • Patchogue PhilPatchogue Phil Member Posts: 265
    Gate valves

    Close the gate valves to the system. Lucky you, I'm never that lucky.

    I put the gate valves in to isolate the boiler w/o having to drain all the zones.  Got the idea from one of Dan's books.

    Thanks for the advice;  I was hoping that would work.
  • icesailoricesailor Member Posts: 7,265
    Gate Valves, Flow Valves:

    The only valves I care about is the flow check and if there's a ball or gate valve on the return with a boiler drain above it so I could purge it without going upstairs.

    If you're as quick as my cat, you can change it with very little lost water. The trick is to drain it into a 5 gallon bucket and when the flow stops, that Higher Power up there is holding up the water for me.

    Quick as my cat, I have it changed.

    A well thought out negative pressure can be your best friend in a pinch.
  • ZmanZman Member Posts: 3,561

    You do understand that if that doesn't work you will be in the exact same predicament you would be in if you followed my advise (which you mocked).

    There is nothing funner to watch than folks in the north east getting fired up about the weather. Most storms that constitute a federal emergency in the northeast would not cancel school in the west.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Patchogue PhilPatchogue Phil Member Posts: 265
    not mocking you

    Not mocking you at all.

    10*F ,  wind chill in negative F numbers,  a foot of white-out snow blizzard with no heat is not fun no matter where you live.   

    I am not panicking at all,  but no reason to go out and drive in those conditions unless you are a first-responder.  With a 4x4. 
  • Patchogue PhilPatchogue Phil Member Posts: 265

    Forgot about this post. End of Summer, I closed the isolation gate valves. Relieved the pressure. Removed old boiler drain with bucket under the area. Maybe half a quart of water burped out. Had a new BD at the ready with threads coated with sealer. Tightened up. Opened refill valve. Re-opened all gate valves. No problems.

  • icesailoricesailor Member Posts: 7,265
    Works every time. Huh Phil.

    As far as Northeasters, out the East end of the Island of Long and farther to the NE, on those Islands that were once part of New York, they get Northeasters that blow harder than Hurricanes, regularly. The Natives hardly notice. Unless it is to go down to the shore and look at the big ocean swells.

    Hurricane Sandy was barely a zephyr compared to some I've seen. Seen it unravel a crow bar once, I did.
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