This winter I noticed a faint noise from the baseboard heat in our house (gas-fired boiler with two zones- one for upstairs and one for downstairs). I suspected air in the lines so I bled them out. I’ve done this quite a bit since we moved in because we’ve rearranged the locations of the baseboards to facilitate a kitchen remodel. Sure enough, there was air in the pipes. After bleeding the pipes, the faint noise was gone but now when the heat kicks on, I hear water gurgling through the pipes. Again, I figure there’s still air in the system so I bleed it again but it doesn’t seem to improve the situation. The gugrling goes away about 10 minutes after the heat comes on but the initial noise is pretty anoying.
I’ve repeated this procedure probably a dozen times over the last week to no avail. I’ve not noticed any leaks in the system either. Everytime I open the spigots to bleed the system, there’s a lot of air. I guess my question is this: is there something basic I should be checking on the system that may be malfunctioning and allowing air into the pipes? Since we’ve lived in this house, I’ve completely drained the system and refilled it several times and have never had this much trouble with air in the lines. The system is set up with an automatic fill valve from the city water supply if that makes any difference. I’d appreciate any suggestions. Thanks.
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You should also post your question at this link. Good bunch of folks. Kinda the plumbing version of this forum.
Water contains about 7% disolved oxygen. When you heat it up it comes out of solution.Best remedy is a spirovent.Assuming you have a diaphragm expansion tank.
Thanks for the response. If a spiro vent is what I think it is (cylindrical thing about the size of a pill bottle and is threaded into top of expansion tank- it has a cap nut on top that is normally left loose), I have one. And, yes there is an expansion tank.
A few other clues: I've noticed a constant wet spot on the side of the boiler by the pressure relief and the relief valve seems to be a little wet. I'm wondering if it's stuck open a little and is letting water out and air in? I'm also noticing that the 2nd floor is overheating (up to 80 degrees when the set point is 73). The second floor recirculating pump is off so I'm assuming the thermostat and the boiler are talking to each other but I'm still feeling a lot of residual heat coming off the 2nd floor radiators. I'm wondering if there's a big slug of air in the first floor loop and it's redirecting heated water intended for the first floor loop up into the second floor loop. Does that sound possible? I'm almost ready to call in a pro but the DIY part of me is hard to beat down...
After several years of head-scratching and plenty of friendly advice from The Wall (at HeatingHelp.com) along with buying and reading most of Dan Holohan's books, here are some tidbits to pass along from a homeowner with a gas boiler/baseboard system that has been hands-off for 4 years except for the annual thermocouple replacement.
First thing you want to do is a thorough examination of all distribution piping that is running through your house and locate ALL bleeder valves.
Some may be hidden between floors and accessible through a hatch.
Just make sure you know where all the bleeders are.
Air can get trapped and prevent water from circulating through spots that you miss.
Second thing is to MAKE SURE the pressure reducer/automatic feed valve assembly is in good working order, especially if it is left open. If you're not sure of its age or condition, replace it.
(There are two opposing viewpoints on leaving the fill valve open or closed after the system is filled.)
If not, it's kinda tricky refilling the system, bleeding, and setting the system at the correct pressure.
Initial system pressure need to be set during refilling while the system is cold, with subsequent bleeding and topping off the system after several heating cycles.
This is especially so with a steel expansion tank system.
When bleeding air, watch the system pressure and make sure makeup water is introduced.
See if there is a Bell & Gossett Airtrol Tank Fitting on your steel tank, if that's what you have.
This item is a must for easily maintaining the correct air/water level in the tank.
A seeping relief valve can mean the tank is waterlogged and there is no air cushion for the water to expand against.
If you have a steel expansion tank setup (vs. a bladder tank), there should not be a airscoop/bleeder setup.
These are just a handful of suggestions.
However, there's a lot of voodoo modifications and repairs done to boiler systems so nothing's ever cut-n-dry when you're trying to figure out what's going on with any given hotwater heating system.
(I ended up correcting several things that were done wrong when our house was switched to a gas boiler/circulator setup from the original oil/gravity system before we bought our house.)
Are there any under-slab runs of heating pipes ?
If you start asking questions, especially at boards such as The Wall, it helps to first have a good understanding of your current setup (plumbing around your boiler) so it can be clearly desribed and understood by the experts.
If you have a digital camera, picture of your boiler plumbing speaks volumes and can speed up the help process.
I also highly recommend Dan Holohan's books, which were recommended to me by other folks.
Good luck.
The pill bottle is a air vent and a relief valve should never leak. Sounds like the best thing to do is go to the Wall and snoop around and once you are comfortable with how the system should run, find a good boiler tech.
Got one lined up for Tuesday morning. I'll post the diagnosis for those interested. Thanks for the suggestions.
An update for those interested. The pressure relief valve was worn out and would automatically release at 20 psi (instead of the designed 30 psi). The service guy said that the 10 psi difference makes it very difficult to bleed air out of the system. The more pressure you can use to bleed the air out, the more effective it will be. So, new relief valve and they also replaced the spirovent (sp?), which are apparently very prone to clogging up after 3-4 years. Works like it always used to now. $311 total damage. I guess I could have taken care of that stuff myself but I didn't know exactly what was wrong until they diagnosed it plus I learned some new techniques for bleeding air out. Thanks again to those who responded to my pleas.