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Dark brown tar like substance dripping from drain valve...

genericnj Member Posts: 70
I have a 30 year old Burnham boiler for a hot water baseboard system. I serviced it myself a few months back, including replacing circulator pump, feeder, back flow preventer, etc. In the process I drained some water and refilled, water appeared clear and not rusty looking. Today I noticed one of the 2 drain valves that are capped off are leaking what looks like very dark brown and sticky residue.. It does not look very fresh and may have leaked out a couple months ago before I noticed, also it is not a lot of leaking, just what I see on the top of the boiler in pictures. Why does this look like tar? Does this indicate my water in the boiler is like this as well? should I drain and refill? Boiler has been working perfectly since I serviced it. thanks all.


  • hot_rod
    hot_rod Member Posts: 18,820
    Yes the water in boilers will take on whatever was or is in the system. Unless cleaned with a hydronic detergent, new systems have oil, flux, solder, grease, pipe dope, etc in them. So the water becomes a blend. Usually enough water in the system dilutes that, but a good cleaner and then flush could in fact help efficiencies a bit, cleaner the boiler and heat emitter walls.

    The gunk in the water will settle to any low points like valves. I suspect if you ran a cup or more out it would be much cleaner.

    A good procedure would be to inject a cleaner, it comes in aerosol cans now with a hose connection to inject. Run that cleaner hot for a few days or a week. Flush it out, put in good, not hard, water. I then like to add a conditioner that coats the bare metals, balances ph, and scavenges excess oxygen.

    These kits contain a cleaner and the final inhibitor. They will do systems with around 35 gallons of water. I like this brand, find them online.

    I'd like to see a better air purger, that one is not installed in the best location, it needs at least 18' of straight pipe upstream to even have a chance. A good microbubble type will get all the air out. Air contains O2 which contributes to ongoing corrosion. A good purger gets and keeps all air out. That would involve some repiping however.

    Once you get the fluid back to good condition, leave it. No need to ever flush it out. Test kits are available to check a sample every few years, add a small boost if needed.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • HomerJSmith
    HomerJSmith Member Posts: 2,022
    edited April 2022
    Do you have anti-freeze solution that is too old in your boiler? Time for a cleaning?

    Replace with de-ionized or distilled water corrected to a PH of about 8-8.5.
  • genericnj
    genericnj Member Posts: 70
    Thx for the replies and info.

    Do you have anti-freeze solution that is too old in your boiler? Time for a cleaning?

    Replace with de-ionized or distilled water corrected to a PH of about 8-8.5.

    I honestly am not sure if there is antifreeze in it, very well might be. When I was doing maintenance the water had a slight pinkish huge but very very slight and only visible if you filled a milk jug with it, but again looked very clear overall and did not have any debris or anything. If there was antifreeze in it, which is likely given I'm in northeast and the pipes do run through the slab foundation so the previous owner may have had it filled, but most of it probably is gone given I drained part of the boiler and refilled a few times while doing the various maintenance items.

    I'm wondering if as Bob mentioned it is old oils and such that settled in those valves and eventually leaked into the caps and stayed there for a long time (I never removed those caps given how crusty they look) and now when those caps decided to leak some of that goo came out maybe... I ran the system all night, but haven't seen any fresh droppings so I feel inclined not to touch them...

  • HomerJSmith
    HomerJSmith Member Posts: 2,022
    Cryotek 100 anti-freeze has a reddish hue.