Continually having to bleed a radiator.....

[firebladerrw]

Some advice please:

I have an open vented central heating system, using a condensing boiler located downstairs in a utility room. My property is a four bedroom detached house with 10 radiators. The system pump is in an upstairs airing cupboard, and the header tank is in the attic. The whole system has recently been flushed and refilled with inhibitor. It also has a filter fitted.

One of the radiators (a towel radiator) is located in the downstairs utility room and requires bleeding almost weekly. I've tried Aladdin auto bleed radiator valves, but they didn't work too well, and I still needed to bleed weekly. All the radiators seem to be fine.

Any suggestions, solutions or ideas?

Thank you

 

[footprints]

Two possible causes,
Leakage leading to constant topping up of water.
Air entering the system most often by the system "pumping over" into the header (F&E) tank or air being sucked down the expansion pipe.

Try turning off the feed to the expansion tank noting the water level (do it either hot or cold to allow for expansion) check frequently to see if it drops if so you have a leak.
Part fill a container with water from the tank (jam jar, jug the old milk bottle was ideal) push it up over the expansion pipe that discharges above the water level in the tank so the pipe is near the bottom, get an assistant to turn on and off heating, hot water to try all options. If the water is sucked into the pipe it is sucking in air if the container oveflows it is pumping over. a change of an inch or so can be ignored.
Try that and post the results then the options can be explained by one of us

 

[firebladerrw]

Two possible causes,
Leakage leading to constant topping up of water.
Air entering the system most often by the system "pumping over" into the header (F&E) tank or air being sucked down the expansion pipe.

Try turning off the feed to the expansion tank noting the water level (do it either hot or cold to allow for expansion) check frequently to see if it drops if so you have a leak.
Part fill a container with water from the tank (jam jar, jug the old milk bottle was ideal) push it up over the expansion pipe that discharges above the water level in the tank so the pipe is near the bottom, get an assistant to turn on and off heating, hot water to try all options. If the water is sucked into the pipe it is sucking in air if the container oveflows it is pumping over. a change of an inch or so can be ignored.
Try that and post the results then the options can be explained by one of us

Thank you. I'm probably being very thick, but I'm not understanding the second paragraph , could you explain it more please.

Thanks

 

[footprints]

If you want to find out the cause of constant air entry thats the way to do it. The air normally tends to
gather in one radiator in your case it is the one you keep bleeding

 

[firebladerrw]

If you want to find out the cause of constant air entry thats the way to do it. The air normally tends to
gather in one radiator in your case it is the one you keep bleeding

Cheers. Read it again and understand. Stick the pipe into bottle with water in it, fire up the system & watch what happens.. ty

 

[footprints]

 

[firebladerrw]

Ok so I did as advised above, and the overflow pipe sucked around 3" out the half filled jar? After about a minute, some water went back in but not very much.

Thoughts?

 

[firebladerrw]

Ok so I did as advised above, and the overflow pipe sucked around 3" out the half filled jar? After about a minute, some water went back in but not very much.

Thoughts?

P's the pump is on minimum speed, before anyone asks

Thanks​

 

[firebladerrw]

Anyone? Thanks

 

[footprints]

Sorry for delay I was away from civilisation (north of the Thames ) for a few days!

It sounds as though possibly you do have some problem with the cold feed/vent connection although not too bad, but do check if the system is loosing water by shutting off the supply and checking the level as I suggested.

If not chances are there is a passage of water being pushed up and down the open vent and feed allowing water with air in it to enter the system.

In theory once the system is filled with water a tiny bit of scale will get deposited, but no more after that. Likewise any oxygen in the water will find it's way out or used up in causing a bit of corrosion, but again once that has occurred no more rusting will happen until the water is replaced by evaporation (very little in a properly covered tank), leakage or draining and refilling.

However if water can circulate through the tank it will pick up oxygen and cause problems.
It can be a real nightmare to trace the trouble, the pipe work should be correct, that is the cold feed and open vent should enter the system within 150mm of each other (ideally in a section of 28mm pipe but usually it is 22mm) on the same side of the pump. (Ideally on the inlet side) so that whatever suction (or the opposite blowtion) affects one will equally affect the other so no movement other than perhaps a slight bob in the water level should occur.
A black hard deposit Magnetite which is a form of rust can build up at the point where the cold feed enters the system causing blockages and affecting the balance between the two pipes.
Take a look at this site it has a diagram showing how the pipes should be and try to figure if yours is correctly piped up for starters.

http://www.home-heating-systems-and-solutions.com/diy-heating-plumbing-tips-6.html

 

[firebladerrw]

Sorry for delay I was away from civilisation (north of the Thames ) for a few days!

It sounds as though possibly you do have some problem with the cold feed/vent connection although not too bad, but do check if the system is loosing water by shutting off the supply and checking the level as I suggested.

If not chances are there is a passage of water being pushed up and down the open vent and feed allowing water with air in it to enter the system.

In theory once the system is filled with water a tiny bit of scale will get deposited, but no more after that. Likewise any oxygen in the water will find it's way out or used up in causing a bit of corrosion, but again once that has occurred no more rusting will happen until the water is replaced by evaporation (very little in a properly covered tank), leakage or draining and refilling.

However if water can circulate through the tank it will pick up oxygen and cause problems.
It can be a real nightmare to trace the trouble, the pipe work should be correct, that is the cold feed and open vent should enter the system within 150mm of each other (ideally in a section of 28mm pipe but usually it is 22mm) on the same side of the pump. (Ideally on the inlet side) so that whatever suction (or the opposite blowtion) affects one will equally affect the other so no movement other than perhaps a slight bob in the water level should occur.
A black hard deposit Magnetite which is a form of rust can build up at the point where the cold feed enters the system causing blockages and affecting the balance between the two pipes.
Take a look at this site it has a diagram showing how the pipes should be and try to figure if yours is correctly piped up for starters.

http://www.home-heating-systems-and-solutions.com/diy-heating-plumbing-tips-6.html

Thanks for the comprehensive reply, I'll check all of the above.

Separate question, I've a potterton condensing boiler, around 5 years old. If the boiler is capable, could I convert to a pressurised system, that is the radiators, pipework and the coil for HW? And if so, what's involved. I don't want a pressurised tank system.

Thanks

 

[footprints]

Assuming as you say the boiler is compatable I would imagine most modern ones would be, the small tank in the loft is removed and replaced (usually somewhere else in the house) with an expantion vessel and a removable filling loop to the mains. A pressure release pipe and valve is run to outside. It is a good idea to replace any old rad valves at the same time as the increase in pressure can cause leaks. Strictly it is a sealed system rather than pressurised as such, it only runs at about 1 to 1.5 bar (a good mains pressure in your cold supply will be maybe a bit over 3 bar) it should solve any problems of air being drawn in.

 

[firebladerrw]

Assuming as you say the boiler is compatable I would imagine most modern ones would be, the small tank in the loft is removed and replaced (usually somewhere else in the house) with an expantion vessel and a removable filling loop to the mains. A pressure release pipe and valve is run to outside. It is a good idea to replace any old rad valves at the same time as the increase in pressure can cause leaks. Strictly it is a sealed system rather than pressurised as such, it only runs at about 1 to 1.5 bar (a good mains pressure in your cold supply will be maybe a bit over 3 bar) it should solve any problems of air being drawn in.

Excellent thanks. I think I'm going to investigate this further. All the rad valves are no more than 3 years old, and most of the radiators have been replaced. Could the expansion vessel, filling loop and pressure release line be fitted in the attic? That is, smply fit the filling loop onto the old CW feed along with expansion vessel and pressure release line?

Lastly, likely cost?

Thanks

 

[footprints]

No idea of cost really I'm afraid well out of touch with current prices now, just get a couple of quotes and see how you go, maybe contact the company that installed the boiler/rad valves.
I guess the vessel could go in the loft, only downside is when the system needs topping up (maybe once a year or so) and there is a pressure gauge to keep an eye on, you will have to get in the loft to check it, also the safety discharge valve will need piping to outside.
No real problem though.