Back boiler air lock

[Paul holley]

Hi all 

I’m new to the forum and I’ll probably find that this question has been answered before I have aback boiler stove feeding my calorifier with a pump in line but am faced with an air lock has anyone got any suggestions as in how to shift this as I’m in dry dock and can’t run my engine for hot water.

 

thanks in advance 

paul

[Mitchellmoxo]

Slightly open a nut at the highest point in the system and ensure there is water getting into the system somehow replacing the air 

[MtB]

Do you know for certain it is an air lock not a physical blockage, or is an air lock an assumption. What are the symptoms? 

 

Running the pump will usually shift an air lock. I presume you have tried this? Another way is to fill the system from the bottom, using a hose attached to the drain cock.

 

Welcome to the forum, by the way. 

[Jen-in-Wellies]

Has the stove/back boiler/circulation system worked well in the past, or is it a new, or new to you system?

How many radiators are in the system, or is it just a calorifier?

 

Further to the first reply, the highest point in the system while the boat is in dry dock won't necessarily be the same as when it is on the water. Assuming it is a flat baseplate steel boat it'll be flat in the dock and trimmed bow up in the water, so the behaviour may change and air may collect in unexpected places.

 

Jen

Edited August 29, 2018 by Jen-in-Wellies

[Paul holley]

Hi all

thanks for your replies and on further in spection I fear I have a blockage as I’m only getting water from one drain off valve that being the one at the highest point, the system has no radiators but has a pump I think the way may be to flush the system as suggested by mike the boiler man unfortunately there seem to be no drain offs on the lower pipe work so I may have to disconnect both pipes going into the back boiler and flush from there. 

Ant further suggestions greatly received, and thanks for all replies so far.

 

I’ll keep you all posted with updates.

 

regards paul

[Jen-in-Wellies]

Hello Paul,

What symptoms are you seeing? Are you getting a sort of banging noise? Just wondering if the water is boiling in the back boiler, filling the top with steam. Gives a similar effect to a blockage. Can also happen if the pump isn't actually pumping. Depends on the system, but the calorifier on its own may not be enough to dissapate the heat, especially once it warms up if it doesn't have extra radiators. What model stove is it? Again, is this a new system, or new to you on a recently purchased boat? Has it worked well in the past to your knowledge?

 

Jen

[Paul holley]

Hi jen

The system is an existing system that worked before as I purchased the boat from a friend I’m at work at present so am not able to look as to what make the stove is as for the pump it seems to be working as you can feel movement on the pipes I cracked the drain off closest to the calorifier but had only the slightest of trickles both with the pump on and off which makes me think it’s a blockage.

ill post the stove make later again thanks for all members help.

regards paul

[WotEver]

5 hours ago, Paul holley said:

unfortunately there seem to be no drain offs on the lower pipe work...

Cut the pipe and fit one?

[MtB]

1 hour ago, WotEver said:

Cut the pipe and fit one?

 

Or even fit one without cutting the pipe first!

 

 

https://www.screwfix.com/p/self-cutting-drain-cock-type-a-15mm/9543r

[WotEver]

I used to have something like that for an outside tap. Didn’t know they came in drain plug stylee...

[Paul holley]

thanks chaps I’ve just found one with a 22mm adapter would this be suitable with pressure from the pump and heat mike??

 

regards Paul

[MtB]

38 minutes ago, Paul holley said:

thanks chaps I’ve just found one with a 22mm adapter would this be suitable with pressure from the pump and heat mike??

 

regards Paul

 

Yes it will. The pressure from the pump is trivial, and all copper pipe fittings are good for 100C.

[Paul holley]

Thanks mike

would I need the pump on while flushing the system.

 

regards Paul 

[MtB]

18 minutes ago, Paul holley said:

Thanks mike

would I need the pump on while flushing the system.

 

regards Paul 

 

Now there's a question. Depends what you mean by 'flushing the system', exactly. What will you be doing to flush it? 'Flushing the system' is a hit and miss affair at best, and a complete waste of time and effort at worst. Run it for a bit, then stop running it for a bit during flushing.  Best of both worlds!

 

If you have a physical blockage and have managed to prove it, best to just . cut the pipes open and remove the blockage. 

[Paul holley]

Hi mike 

i was thinking of connecting a hose at the lowest point where I’ll connect one of the self tapping valves and a pipe to drain at the highest point of the system having closed of the header tank and just let the hose run till it runs back freely.

 

does this sound like the right way to go ??

 

regards Paul 

[MtB]

1 minute ago, Paul holley said:

Hi mike 

i was thinking of connecting a hose at the lowest point where I’ll connect one of the self tapping valves and a pipe to drain at the highest point of the system having closed of the header tank and just let the hose run till it runs back freely.

 

does this sound like the right way to go ??

 

regards Paul 

 

Well the obvious problem here is you are trying to flush a circuit, so there must be two routes up to the top of the system, one of which you say is blocked. The water you re flushing with, is going to choose the unbocked route don'tcher think??

[BWM]

9 hours ago, Paul holley said:

Hi all

thanks for your replies and on further in spection I fear I have a blockage as I’m only getting water from one drain off valve that being the one at the highest point, the system has no radiators but has a pump I think the way may be to flush the system as suggested by mike the boiler man unfortunately there seem to be no drain offs on the lower pipe work so I may have to disconnect both pipes going into the back boiler and flush from there. 

Ant further suggestions greatly received, and thanks for all replies so far.

 

I’ll keep you all posted with updates.

 

regards paul

The item at the highest point is more likely to be a bleed valve rather than a drain. If you have water exiting then an airlock is unlikely. 

7 hours ago, Paul holley said:

Hi jen

The system is an existing system that worked before as I purchased the boat from a friend I’m at work at present so am not able to look as to what make the stove is as for the pump it seems to be working as you can feel movement on the pipes I cracked the drain off closest to the calorifier but had only the slightest of trickles both with the pump on and off which makes me think it’s a blockage.

ill post the stove make later again thanks for all members help.

regards paul

The pump may still vibrate long after it stops moving water, it would be wise to test it after you have fitted a drain at the lowest point. When draining you will need to open the bleed valve at the top at the same time. Who knows, if the system has never been drained it may move any blockage?