Air getting into CH system

PeteFalk78

Hi,

Firstly I'm a complete plumbing novice. I don't know if we have an open system or a closed system. We have a small water tank in attic beside the main water tank - does this mean it's an open system?

Anyway I have the CH and hot water zoned separately. Every week or two I have to bleed the radiator in my utility - it could be 1/2 full of air. This time of the year I'm just using the boiler for hot water but I can hear the air bubbles going through the pipes. There is no visible water spots in the house - I've no idea where the air is getting in.

I guess its coming from out near the boiler or from the tank in the attic (but that is always full). Can I let all the air of the system at the boiler end? I can post a picture later when I get home if it helps.

Thanks.

Sleeper12

You have a leak somewhere. Air can only get into the system if water leaves.

Check all the valves & fittings that you can find for drips or weeping. This must be done with heating turned off for a few hours. Hopefully it won't be under ground or under floors.

Cerco

Would pitching cause air in the system?

Wearb

Do you have a boiler stove?

PeteFalk78

Wearb wrote: »

Do you have a boiler stove?

Thanks for all the advice guys.

Nope I only have an oil burner. The boiler is in an outdoor pumphouse around 15 foot from the house. I'm pretty happy that the leak isn't indoors - no staining on ceilings or wet ground anywhere.

I'll check out at the boiler again to ensure there are no leaks there.

Cerco wrote: »

Would pitching cause air in the system?

No idea what that even is

Wearb

Have someone stay up in the attic with a flash lamp and watch for water coming out the pipe hooked in over the small tank. Also watch for water going out the overflow. While that person is watching, run you heating system in all the configurations that you normally run it. E.G. heat only, hot water only, both, some rads off, etc. Whatever different ways you normally do.

Wearb

Also check the air vent and pressure relief valve (don't touch it, just look) on top of the boiler for leaks.

PeteFalk78

Wearb wrote: »

Have someone stay up in the attic with a flash lamp and watch for water coming out the pipe hooked in over the small tank. Also watch for water going out the overflow. While that person is watching, run you heating system in all the configurations that you normally run it. E.G. heat only, hot water only, both, some rads off, etc. Whatever different ways you normally do.

Thanks I'll try that and will report back.

I've checked the boiler and cannot see any leaks. I've just got it serviced today and the service engineer didn't find anything. I'm pretty sure that the air is mostly in the first radiator downstairs on the line and the first radiator in the line upstairs. I've just bleed the downstairs radiator and it was 1/4 full - I hear mild clanking in it when heating is on. It's looking more and more like a leak between pumphouse and house

Here is my boiler

Wearb

I also forgot to say to keep an eye out for water coming in the ball valve on that tank

ray.g

As another poster said the only way to make 100% sure that it is a leak is to monitor the expansion tank. By the sounds of what you are saying it is a very small leak and it may take a few days to prove it. Check all you can above ground for dampness. Then tie up the ballcock and measure the depth if water. Check to see if it drops over the next few days

PeteFalk78

Ok I've tied up the ballcock in expansion tank. Will check it again tomorrow or Friday. Can I bleed any air out via the pump (is that the red thing at the right of the pic above) and can somebody explain what is at the top left of the pic above. When I push or twist that a small bit of water comes out.

Wearb

You would only bleed a little air out (air that in the pump only) via the pump. The thing on the top left is a pressure release valve and I would normally leave them alone. They often leak after activating. If you got water out of it, then there isn't air there.
Water may drop in the small tank where you tied up the ball valve if the system water is at a lower temperature when next checked, than it was when you tied it up.

You may end up having to get someone experienced in these things in the end.

PeteFalk78

Wearb wrote: »

You would only bleed a little air out (air that in the pump only) via the pump. The thing on the top left is a pressure release valve and I would normally leave them alone. They often leak after activating. If you got water out of it, then there isn't air there.
Water may drop in the small tank where you tied up the ball valve if the system water is at a lower temperature when next checked, than it was when you tied it up.

You may end up having to get someone experienced in these things in the end.

Thanks for your help Wearb. I'll give my plumber a shout once I've verified the water level drops in the expansion tank.....well I suppose it absolutely has to drop as air is constantly getting into my system. I'll keep this thread updated for future use.

ray.g

Wearb wrote: »

You would only bleed a little air out (air that in the pump only) via the pump. The thing on the top left is a pressure release valve and I would normally leave them alone. They often leak after activating. If you got water out of it, then there isn't air there.
Water may drop in the small tank where you tied up the ball valve if the system water is at a lower temperature when next checked, than it was when you tied it up.

You may end up having to get someone experienced in these things in the end.

Good point, forgot to mention to do this when the system is cold

dersawazzie

Just because you have 'air' in your system, this doesn't necessarily indicate a leak. A sludged system causes a gas to form, poorly piped systems can suck air in via the open vent. This is just an alternate view, so don't panic it may not be a leak. Your plumber should be able to identify the issue relatively quickly.

Dtp1979

dersawazzie wrote: »

Just because you have 'air' in your system, this doesn't necessarily indicate a leak. A sludged system causes a gas to form, poorly piped systems can suck air in via the open vent. This is just an alternate view, so don't panic it may not be a leak. Your plumber should be able to identify the issue relatively quickly.

You took the words right out of my mouth. Also check auto air vents, sometimes, if placed in incorrect positions they can actually suck air into the system

PeteFalk78

Dtp1979 wrote: »

Also check auto air vents, sometimes, if placed in incorrect positions they can actually suck air into the system

Sorry could you elaborate on this? I've no idea what these are.

Dtp1979

PeteFalk78 wrote: »

Sorry could you elaborate on this? I've no idea what these are.

They're usually brass, cylindrical, with a black or red or brass screw cap on top. The screw cap is very similar to the caps you find on the air valves on your car tyre.
Make sure these are closed

PeteFalk78

Dtp1979 wrote: »

They're usually brass, cylindrical, with a black or red or brass screw cap on top. The screw cap is very similar to the caps you find on the air valves on your car tyre.
Make sure these are closed

Thanks dtp, I don't I've seen these anywhere on my system.

Dtp1979

PeteFalk78 wrote: »

Thanks dtp, I don't I've seen these anywhere on my system.

Usually at the boiler and hot press. Maybe the attic too depending on the pipe work

PeteFalk78

Ok results from tied up expansion tank ballcock shows a drop of maybe 2 pints of water a week. I cannot find any air vents on my system.

Anyway I've contacted my plumber (they guy who put in the system originally) so hopefully will get to the bottom of it soon.

Wearb

Its not a very big leak. Has the system been running while the ballcock was tied up? Did you check water level with system off and cold, both at beginning and end? Did you ever check for pumping over?

If you have cold spots at bottom centre of any rads, you may need to flush it after fixing the leak, if it is a leak. And add inhibitor.
Hope you get it sorted.

PeteFalk78

Wearb wrote: »

Its not a very big leak. Has the system been running while the ballcock was tied up?

I've been running the hot water from it - e.g. I have valves for downstairs and upstairs radiators closed from timer.

Wearb wrote: »

Did you check water level with system off and cold, both at beginning and end?

Yes the system was cool on both times.

Wearb wrote: »

Did you ever check for pumping over?

Sorry can you explain this to me a bit?

Wearb wrote: »

If you have cold spots at bottom centre of any rads, you may need to flush it after fixing the leak, if it is a leak. And add inhibitor. Hope you get it sorted.

Thanks for your help Wearb (and others). Much appreciated.

Wearb

Pumping over was mentioned in my first answer. It refers to water coming out the open ended pipe hooked in over the small tank.

Dtp1979

If you had it tied up for a week, and it was quite warm recently, maybe evaporation could be a major factor too.
The only way to know for sure is to get it pressure tested

walus

Not to hijack the thread but I have a very similar problem to the OP here. I'm after moving into a newly refurbished house with upgraded 3 zone central heating system. I'm getting a constant influx of air into the first radiator in the circuit upstairs. The main reason I noticed it is that after bleeding it the next system turn on for the upstairs zone is noise free - no gurgling or other noises associated with the water flow. The second and subsequent firings cause noise to the extend that they wake me up in the morning. I can see the water flowing through the radiator for the first 10 seconds after turning on the heating in that zone. None of the downstairs radiators gets any air in. I'm running the pump on #1 setting and before it was #3 which caused most of upstairs radiators to fill up with air. I know very little on central heating systems but am an engineer and I'd like to get to the bottom of any problem by nature. I know that running the pump on to high of a speed can cause cavitation and that is why I reduced its setting. It sort of had an impact but did not cure the problem. I tied the ball cock valve at the expansion tank and over a week the level of water dropped maybe by half a pint. Not sure how representative of a leak that is. The system sucks in air somewhere and I'm running out of ideas as how and where it is. Could you guys suggest the next step I could do myself to determine what could be wrong with my ch system? Thanks.

Sleeper12

Air being lighter than water rises to the top of a rad. Likewise on a bigger scale air will always always make its way to the top of the heating system. If you had a rad in the attic then thats the one that would have the air.