Central Heating. Cold and Noisy Rads

Aeneas

I have an oil fired heating system with 14 rads and the following problems.
-two radiators - one upstairs, one downstairs - need bleeding every few days
-several of the rads upstairs are tepid rather than hot, bleeing them makes no difference,
-one of the downstairs rads has constant rushing or gushing noise when turned on,
-all the rads have a low level hissing noise when the heating is on,
-one of the rads has a constant clicking sound when the heating is on.
I have had the system balanced but these problems remain. I suspect a leak but before I begin to take up floorboards and dig up concrete I would like to know whether there might be a simpler explanation. Also, is there a way to check for leaks without digging up my concrete floors downstairs?

JamesM

Aeneas wrote:

I have an oil fired heating system with 14 rads and the following problems.
-two radiators - one upstairs, one downstairs - need bleeding every few days
-several of the rads upstairs are tepid rather than hot, bleeing them makes no difference,
-one of the downstairs rads has constant rushing or gushing noise when turned on,
-all the rads have a low level hissing noise when the heating is on,
-one of the rads has a constant clicking sound when the heating is on.
I have had the system balanced but these problems remain. I suspect a leak but before I begin to take up floorboards and dig up concrete I would like to know whether there might be a simpler explanation. Also, is there a way to check for leaks without digging up my concrete floors downstairs?

It could be a leak, especially when a downstairs rad has air.
Is your system loosing water ? Do you have a sealed system or is there a header tank in the attic ?
Find where the system is filled and shut it off. If things get worse, then the water is going somewhere.
Jim.

Aeneas

Thanks Jim. It's an open system fed from a small tank in the attic. So I guess I should tie up the ball cock and see what happens. If the leak were upstairs I imagine I would see evidence of it in the ceilings at this stage. Downstairs most of the pipes are buried in the concrete floors. Again there is no evidence of leaks - wet carpet etc - but perhaps the piping is deep and the water seeps down through the concrete. Is there any way to find a leak short of digging up all the concrete floors downstairs?

JamesM

Aeneas wrote:

Thanks Jim. It's an open system fed from a small tank in the attic. So I guess I should tie up the ball cock and see what happens. If the leak were upstairs I imagine I would see evidence of it in the ceilings at this stage. Downstairs most of the pipes are buried in the concrete floors. Again there is no evidence of leaks - wet carpet etc - but perhaps the piping is deep and the water seeps down through the concrete. Is there any way to find a leak short of digging up all the concrete floors downstairs?

Is your boiler inside the house or outside ? The most likely place for a leak is where the pipes run in from a boilerhouse away from the house.
If the leak is very bad, you should see water dripping into the header tank. from the ball cock. If there is a leak under the floor, it is likely near the downstairs rad which has the air in it.
Can't think of anything else at the moment
Jim.

Aeneas

The boiler is outside. No boilerhouse, one of those standard galvanised housings that you see everywhere. This morning another rad upstairs was completely cold and when I tried to vent it nothing came out - no air, no water - although the system was on at the time.

JamesM

Aeneas wrote:

The boiler is outside. No boilerhouse, one of those standard galvanised housings that you see everywhere. This morning another rad upstairs was completely cold and when I tried to vent it nothing came out - no air, no water - although the system was on at the time.

That's called a "cabinpac"

No Air no water means that, either there is no water getting into the system, or it is getting out faster than it is going in. If this is the case the water must be pouring into the header tank or there is a blockage from the header tank down to the hotpress and the rest of the system. Could there be a valve turned off on the pipe from the header tank down to the hotpress. I presume that you have checked that there is water in the header tank and the ballcock is not stuck in the up position.
To recap: If there is water in the header tank (and it is not continuously filling), and you have nothing coming out the rad vent, then there is a blockage along the pipe from the header tank down towards the hotpress area.
Jim.

Aeneas

I turned on the heating and climbed into the attic. The header tank (I presume this is the small tank that feeds the central heating as distinct from the main water tank) was stable - it was full up to the level of the ballcock and there was no water coming in through the valve. Maybe I should check again after a while. As far as I can see the two valves in the hot press leading to/from the hot water tank are open and we have hot water. But the landing rad is still cold and no air or water escapes when I try to bleed it.

JamesM

Aeneas wrote:

I turned on the heating and climbed into the attic. The header tank (I presume this is the small tank that feeds the central heating as distinct from the main water tank) was stable - it was full up to the level of the ballcock and there was no water coming in through the valve. Maybe I should check again after a while. As far as I can see the two valves in the hot press leading to/from the hot water tank are open and we have hot water. But the landing rad is still cold and no air or water escapes when I try to bleed it.

If it is an old system and everything you say is correct, then the pipe from the header tank is blocked. This often happens with gunbarrel - usually between the tank and where it branches off to the bottom of the hot water cylinder (if that is in the hotpress below the header tank) If you have copper pipes, then look again for a valve on the pipe between the header tank and the branch to the bottom of the cylinder)
Jim.

Aeneas

Thanks Jim. I had a complete new system put in about six years ago when I renovated the house. The pipe leading from the bottom of the header tank consists of a short length of copper (about eight inches) connected to plastic piping which disappears through the attic floor. There is a valve (red circular knob) on this piping at about a foot distance from the tank. It appears to be open.

JamesM

Aeneas wrote:

Thanks Jim. I had a complete new system put in about six years ago when I renovated the house. The pipe leading from the bottom of the header tank consists of a short length of copper (about eight inches) connected to plastic piping which disappears through the attic floor. There is a valve (red circular knob) on this piping at about a foot distance from the tank. It appears to be open.

All you can do is make sure that the valve is turned anticlockwise. Then check on down the pipe and find where it joins the rest of the system - see if there is another valve. Sometimes the inside of the valve can stick and block off the opening - even with the handle in the open position. Also you can get a blockage of dirt where the outlet pipe joins the tank.
Think of the pressure of a tank full of water - a pipe coming out the bottom - joining into the heating system - if there is no blockage, when you open the vent on the rad, air or water has to be pushed out.
Unfortunately you may also have a leak, but first you have to get the system filling.
Jim.

Aeneas

Maybe this is important. The rads downstairs are venting normally - when I open them I get water dripping or spurting out. And they are hot. Upstairs is a different matter. I have five rads - one in each of the two bedrooms, one small one in each of the two bathroom/shower rooms and a mid sized one on the landing. None of these vent normally -no air, no water. One of the bedroom rads (which has to be frequently vented) is hot, the other bedroom rad and the two in the bathrooms are warm. The landing rad which was stone cold earlier now has a little heat in it - tepid. I opened and closed the valve in case their was a blockage at that point and this may have allowed in some hot water. All rads operate off the same boiler and pump. The problem still puzzles me. If there was a general blockage would the downstairs rads operate normally? And if there is a blockage to the upstairs system only why is one of the rads there hot? Maybe its time for a plumber?

Avns1s

Aeneas wrote:

Maybe this is important. The rads downstairs are venting normally - when I open them I get water dripping or spurting out. And they are hot. Upstairs is a different matter. I have five rads - one in each of the two bedrooms, one small one in each of the two bathroom/shower rooms and a mid sized one on the landing. None of these vent normally -no air, no water. One of the bedroom rads (which has to be frequently vented) is hot, the other bedroom rad and the two in the bathrooms are warm. The landing rad which was stone cold earlier now has a little heat in it - tepid. I opened and closed the valve in case their was a blockage at that point and this may have allowed in some hot water. All rads operate off the same boiler and pump. The problem still puzzles me. If there was a general blockage would the downstairs rads operate normally? And if there is a blockage to the upstairs system only why is one of the rads there hot? Maybe its time for a plumber?

It shouldn't really make a difference but are the upstairs and downstairs rads on different zones?

Moanin

Try closing all the rads downstairs and the hot press tank and open all the rads upstairs? Once they have heated after 10 mins or so open all the other rads and tank again?

JamesM

Aeneas wrote:

Maybe this is important. The rads downstairs are venting normally - when I open them I get water dripping or spurting out. And they are hot. Upstairs is a different matter. I have five rads - one in each of the two bedrooms, one small one in each of the two bathroom/shower rooms and a mid sized one on the landing. None of these vent normally -no air, no water. One of the bedroom rads (which has to be frequently vented) is hot, the other bedroom rad and the two in the bathrooms are warm. The landing rad which was stone cold earlier now has a little heat in it - tepid. I opened and closed the valve in case their was a blockage at that point and this may have allowed in some hot water. All rads operate off the same boiler and pump. The problem still puzzles me. If there was a general blockage would the downstairs rads operate normally? And if there is a blockage to the upstairs system only why is one of the rads there hot? Maybe its time for a plumber?

It's quite simple - think of the whole system as one large container holding water. There is a lack of water in the container - it is not full to the top. The water is only coming up to halfway. All the downstairs rads are heating, but there is only a small amount of water above halfway up the container. You need to fill the container, but the water is not getting down from the header tank.
Jim.

Aeneas

Thanks. Sorry to be a bit dumb about this. I see the point about the container. But if the hot water is being pumped around the system why do I only have the problem upstairs.

JamesM

Aeneas wrote:

Thanks. Sorry to be a bit dumb about this. I see the point about the container. But if the hot water is being pumped around the system why do I only have the problem upstairs.

The water is lying in the bottom of the container - there is not enough water to fill the container. The water is being pumped around the downstairs rads. There is no (or very little) water upstairs. The upstairs rads are empty or almost empty - so no heat.
Jim.

Aeneas

Assuming there is a blockage on the pipe from the header tank to the hot water tank, is it a big job to unblock it? Would for example the plumber need to take out the hot water tank and dismantle the piping? I know that a lot depends on individual systems but I'm just trying to get an idea of the complexity and disturbance that may be involved.

JamesM

Aeneas wrote:

Assuming there is a blockage on the pipe from the header tank to the hot water tank, is it a big job to unblock it? Would for example the plumber need to take out the hot water tank and dismantle the piping? I know that a lot depends on individual systems but I'm just trying to get an idea of the complexity and disturbance that may be involved.

You will probably need a plumber. The hot water cylinder should not have to be moved. The pipe from the header tank will have to be dismantled and checked to see where the blockage is. (Unless the problem is obvious to a qualified plumber). Once you have water back in the system, then you can think about finding a leak - although you may not have one at all.
Jim.

Aeneas

Well, I got a plumber, described to him the symptoms of my problem and demonstrated the noise, hissing, venting etc. On the basis of this he declared that I "definitely" had a leak and offered to repipe my entire system (along the skirting and down the walls) to avoid the hassle of digging up floors. Did not look at the header tank and never mentioned the possibility of a blockage. Thanks but no thanks. Anyone know a reliable, qualified and experienced central heating specialist in south Wexford?

GreeBo

If you drain any of the rads downstairs does it start the header tank off?
It doesnt sound like you have a bad leak somewhere, just that as Jim says, you system has been slowly emptying (over the last 6 years?) and has not been refilling itself as it should.

A final test for a blockage is to drain a rad downstairs and see if it has any effect on the filler tank.

If not, tie up the ballcock (or close the valve if it exists) then take apart the connection between the tank and the outlet pipe.

The blockage might just be on this joint (something stuck in the header tank) but you should at least be able to see something.


Depending on your circumstances you can hook up a compressor (1 bar) or even a hose and see if you can force any blockage somewhere.

If your entire heating system is qualpex or Acorn you "should" be able to start dismantling joints upstairs to see where it starts to get dry...bring a bucket!

Aeneas

Thanks. I'm encouraged to think it might be a blockage rather than a leak. And it would explain a lot of the symptoms I have been having. The header tank looks stable and the water mark, from the heavy lime in our water, is visible along the existing water line. If the tank were emptying and filling over the past six years I imagine that the line would either not exist or that there would be several. In addition the rust coloured algae, or whatever it is that grows on the inside of tanks, reaches up to the current water line, as if it has never been disturbed. But maybe this is wishful thinking. There is a valve on the exit pipe about a foot away from the tank. I suppose this would be a first candidate for a blockage. As a first step I could poke (gently) into this with some wire to see if there is anything there.

JamesM

Aeneas wrote:

Thanks. I'm encouraged to think it might be a blockage rather than a leak. And it would explain a lot of the symptoms I have been having. The header tank looks stable and the water mark, from the heavy lime in our water, is visible along the existing water line. If the tank were emptying and filling over the past six years I imagine that the line would either not exist or that there would be several. In addition the rust coloured algae, or whatever it is that grows on the inside of tanks, reaches up to the current water line, as if it has never been disturbed. But maybe this is wishful thinking. There is a valve on the exit pipe about a foot away from the tank. I suppose this would be a first candidate for a blockage. As a first step I could poke (gently) into this with some wire to see if there is anything there.

I wasn't sure how much you wanted to do yourself, but when you come across a plumber like that, maybe you should have a go yourself. You can try poking a wire coathanger (opened out) into the exit from the tank and see if it goes as far as the valve or a bend in the pipe. After that you could try GreeBo's suggestions.
Jim.
It is odd that you have a blockage after only 6 years

GreeBo

JamesM wrote:

I wasn't sure how much you wanted to do yourself, but when you come across a plumber like that, maybe you should have a go yourself. You can try poking a wire coathanger (opened out) into the exit from the tank and see if it goes as far as the valve or a bend in the pipe. After that you could try GreeBo's suggestions.
Jim.
It is odd that you have a blockage after only 6 years

Im wondering has there been a blockage since the start, something sitting in the tank or pipes...

Aeneas, if you close that valve you can take that connection apart, at least then you can visibly inspect one side of the valve and also poke away at a fair section of pipe...

Aeneas

Thanks Jim and Greenbo for your time and advice. I really appreciate it. I realise this exchange can't go on forever and I will have to bite the bullet and get another plumber (hopefully one that won't propose repiping my entire system!). However, I thought I should let you know the results of my latest effort. This morning I poked a lenght of wire (a clothes hanger) down the outlet pipe from the header tank. It went in the full length well past the opened valve. No evidence of blockage at either the exit from the tank or the valve. I then tried the hose pipe suggestion using a hoselock spray for extra pressure (the other resident wasn't very happy to see a dirty garden hose across her kitchen, dining room, stairs and landing). After about thirty seconds there was some kind of blow back - air I think, or it could have been water backing up the pipe. When I vented the upstairs rads after this there was a drizzle of water (but see below). Encouraged, I turned on the heating but unfortunately things are much the same as before. I will describe the current situation in case there are additional clues
1. as a result of the additional water from the hose the header tank is now fuller than it was - up to the overflow pipe, and a few inches above the red algae (or whatever),
2. two of the five upstairs rads are fairly hot, two are tepid and one pretty cold. The inlet (the one with the on/off knob) and outlet pipes to the cool rads are also cool or cold. None of the rads vents properly, not even the two that are hot. No air, no water.
3. nine of the eleven downstairs rads are hot. One is cold and its inlet and outlet pipes are cold. And a second, that was hot until recently, is now only warm.
I'm still hoping it's a blockage and that maybe a plumber could unblock it with some kind of compresser. Or perhaps I should move to a closed system?

GreeBo

No worries..
No need to change systems, this is not a symptom of your system, you are either just unlucky or the victim of a poor install.

I wonder what would happen if you open a vent on one of the rads while attaching the hose?
Maybe its not a blockage but some trapped air that your header tank hasnt the pressure to move?

JamesM

Another track - Is you hotwater cylinder in a hotpress below the header tank ? Any chance of some photos of the pipework in that area ?
Jim.

Aeneas

The "poor install" strikes a chord. Almost all the problems we have had since the renovation have been on the plumbing side (pipes so close to the surface that carpet fitters punctured them; rigid copper pipes fitted to shower motor instead of flexible connections; result copper pipes worked loose from vibration, flooded downstairs room, new ceiling needed; main valve installed behind kitchen cabinets with no access; showers had to be taken down and reinstalled. I could go on...). I think I have found a reliable and experienced central heating plumber who is to coming in the next day or so to have a look. His initial diagnosis is similar to yours - either a physical blockage or a large air lock caused by poor pipework. His feeling though is that even if he unblocks it the problem will probably come back in a few months and he suggested I think of a pressurised system. I will let you know what happens.

rogue-entity

OP, I dont know how your system is plumbed, but since you managed to get water running from the base of your system to the header tank, that you cleared the blockage which I suspect was an airlock.

We had to change our hot water cylinder recently, this ment we had to drain our central heating system as well as the hot water system. With the central heating, we were told to wait for the system to fill and then run the heating system for an hour to pump the water around as it would force the air into the radiators. Two of the radiators downstairs remained cold and wouldnt clear, so I turned off all the ones that worked and a valve connecting them to the upstairs ones. That sorted them for us. And once they started heating, I opened the valve and all but one rad heated up, that one rad was half hot, so I bleed it. ALl was sorted. SO I suggest to you, turn off all the radiators that you know to be heating just fine, forcing the water around to the ones that dont heat. Hopefully this will force the water to run upstairs through the pipes and force the trapped air into the nearest radiator. I would suspect that the pressure in the header tank isnt enough to force out any trapped air in the system, that their isnt a blockage between the tank and the upstairs rads, but that their is an airlock stopping the water getting to the rads, it can happen with a bad pipe run.