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Bleeding a residential HW system

Carlson Member Posts: 1
So...long-time Wall reader looking for some advice.

I'm doing a favor for a friend-of-a-friend who is selling his house. Replacing a leaky gate valve in a 40-year-old hot water heating system. Haven't seen the thing before, but I imagine it's not too highly engineered, being 40 years old, residential, and in a small town. I woudn't be surprised if it isn't even zoned.

Here's my worry. I'll obviously have to drain this system to replace the valve. Then, I'll have to fill it back up. I don't know what kind of heaters he has in there, but if there's no coin vent on them, I'm not sure how I can bleed out the air when the repair is done.

I've only ever worked on industrial systems where all the appropriate valves and drains are specced and installed right there for you. Any advice  from the residential side of heating would be greatly appreciated!

Thanks guys!


  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Lack of coin vents...

    I am not a professional, but my system has no vents except for the one built into the top of the TACO 4900 series air separator (49-125).

    http://www.taco-hvac.com/en/products/4900 Series/products.html?current_category=89#

    Downstairs is copper tubing in a slab. Upstairs is Slant/Fin finned copper tube baseboard. I asked why no coin valves to bleed the baseboard stuff,  and the contractor said baseboard did not need it. They did have separate purge valves for both upstairs and downstairs, and they used them to flush the air from the system. They said the air separator would take care of the rest. And that seems to have been the case.

    If they had not purged the system first, the air separator would never have been able to remove the remaining air because there would have been no flow upstairs. But since they did purge the system, what little air remained dissolved into the water and the air separator removed it, although this took several months (because the system runs at a fairly low temperature: at most 135F). It would probably take only a week or so if the system ran at the more usual 180F.
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