Puzzling plumbing problem
- Thread starter Ianm
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I don't pretend to fully understand your layout and system but the symptoms indicate that you are simply getting an airlock in the HW supply.
To give you an idication I will detail a similar problem many years ago. We had the job of installing HW systems to around thirty bungalow style properties simply consisting of a HW cylinder with an immersion heater and a tank in the roof space.
The only possible route to the kitchen for the HW pipe off the top of the cylinder was to branch it off the expansion in the roof space and run horizontally across the joists and down into the kitchen.
We did the first one and it worked fine but next day it was air locked. Cleared this but in the afternoon it was back again causing us to realise we had to sort this out before doing any more.
The reason was quite simple and it was that as the distance between the draw off on the expansion pipe and the top of the vent pipe was only a couple of feet when a tap was opened the leg of water in this section dropped immediately down to the Tee piece and you could hear the air being pulled in.
The cure was to take the draw off immediately after the expansion pipe left the cylinder and to run it up into the roofspace alongside the vent pipe.
This completely cured the problem.
As said previously I don't understand your system but you certainly have ingress of air into the draw off pipe and a vent is really the only place it can get it.
wemyss
To give you an idication I will detail a similar problem many years ago. We had the job of installing HW systems to around thirty bungalow style properties simply consisting of a HW cylinder with an immersion heater and a tank in the roof space.
The only possible route to the kitchen for the HW pipe off the top of the cylinder was to branch it off the expansion in the roof space and run horizontally across the joists and down into the kitchen.
We did the first one and it worked fine but next day it was air locked. Cleared this but in the afternoon it was back again causing us to realise we had to sort this out before doing any more.
The reason was quite simple and it was that as the distance between the draw off on the expansion pipe and the top of the vent pipe was only a couple of feet when a tap was opened the leg of water in this section dropped immediately down to the Tee piece and you could hear the air being pulled in.
The cure was to take the draw off immediately after the expansion pipe left the cylinder and to run it up into the roofspace alongside the vent pipe.
This completely cured the problem.
As said previously I don't understand your system but you certainly have ingress of air into the draw off pipe and a vent is really the only place it can get it.
wemyss
The suggestion by the plumber / chrisr sound like a good idea and I will try it out. I am not sure what will happen.
wemyss - the problems do sound very similar, but I probably haven't described my system very well. Until recently there was no vent in this part of the system. I put a vent in in the hope that it would cure the problem. The expansion pipe and vent in our hose only exists in the part of the system where hot water comes from the boiler before going to radiators and / or the hot water tank. As far as I am aware this is separate as the hot water tank is heated by convection from the pipes running through the tank (I think).
I've had a look today and can't seen any vent (other than the new one I put in) between the hot water tank and the new pipework which runs to the kitchen. Having said that as you state the only place air can really get in is through a vent so I'm really back to being puzzled
wemyss - the problems do sound very similar, but I probably haven't described my system very well. Until recently there was no vent in this part of the system. I put a vent in in the hope that it would cure the problem. The expansion pipe and vent in our hose only exists in the part of the system where hot water comes from the boiler before going to radiators and / or the hot water tank. As far as I am aware this is separate as the hot water tank is heated by convection from the pipes running through the tank (I think).
I've had a look today and can't seen any vent (other than the new one I put in) between the hot water tank and the new pipework which runs to the kitchen. Having said that as you state the only place air can really get in is through a vent so I'm really back to being puzzled
Ian, I think there is some confusion in our minds as to exactly what kind of system you have.
If we start from basics the normal one is this. You have an heating system and presumably a boiler which heats your hot water through coils in the cylinder. (We don’t call them a hot water tank.)
If this is what you have the following is the norm.
1. You have two systems which are not connected to each other.
2. There is the primary one which is the boiler..the radiators..the flow and return to the cylinder which go through the coil and is supplied from a small tank normally in the roof space and referred to as the make up tank.
3. The other system is known as the secondary. This consists of the hot water in the cylinder and all pipework associated with DHW (domestic hot water) this is supplied from a larger tank in the roof space.
These are entirely separated from each other and never should they mix.
There is a vent pipe over each of these tanks from their respective system and incidentally you must never put a valve on them.
The above may be a little difficult to grasp but these are the basic principles for the majority of systems and I cannot visualise what your system is but if you are putting a another vent or expansion pipe in the system and getting water to run into the tank it could be that you have crossed the two systems, and with the two tanks being at different levels they are trying to equalise the level. That is only a thought but are you sure you haven’t got two tanks and you haven’t spotted the other one yet.?
A common occurrence is that if the coil in the cylinder springs a leak which means the two water systems can mix the lowest tank level will begin to rise as it begins to equalise until it runs through its overflow.
Have another look at your system and describe what you see. Look for another tank and be very wary of putting valves where they shouldn’t be.
wemyss
If we start from basics the normal one is this. You have an heating system and presumably a boiler which heats your hot water through coils in the cylinder. (We don’t call them a hot water tank.)
If this is what you have the following is the norm.
1. You have two systems which are not connected to each other.
2. There is the primary one which is the boiler..the radiators..the flow and return to the cylinder which go through the coil and is supplied from a small tank normally in the roof space and referred to as the make up tank.
3. The other system is known as the secondary. This consists of the hot water in the cylinder and all pipework associated with DHW (domestic hot water) this is supplied from a larger tank in the roof space.
These are entirely separated from each other and never should they mix.
There is a vent pipe over each of these tanks from their respective system and incidentally you must never put a valve on them.
The above may be a little difficult to grasp but these are the basic principles for the majority of systems and I cannot visualise what your system is but if you are putting a another vent or expansion pipe in the system and getting water to run into the tank it could be that you have crossed the two systems, and with the two tanks being at different levels they are trying to equalise the level. That is only a thought but are you sure you haven’t got two tanks and you haven’t spotted the other one yet.?
A common occurrence is that if the coil in the cylinder springs a leak which means the two water systems can mix the lowest tank level will begin to rise as it begins to equalise until it runs through its overflow.
Have another look at your system and describe what you see. Look for another tank and be very wary of putting valves where they shouldn’t be.
wemyss
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Just a thought - how hot is your hot water in the cylinder? If it's very hot - don;t have aspecific figure, you get bubbles in it. If some of them don't make it up the vent you might be getting them collecting in your high point. It's quite common for HW pipes to get air in so the water spurts a bit, even in normal layouts.
Thanks for all the help so far.
Chrisr - the water never gets that hot, but the point you make could still be true.
wmyss - we do have two separate systems, my explanation is obviously not very good and I will try and explain in more detail. The primary system takes water directly from the borehole to the boiler (no tank! - which I believe would be more normal). Pipes from the boiler than run through the radiators and also through the coil in the cylinder (thanks for giving me the correct terminolgy) and back to the boiler. The boiler is situated in an outhouse and the pipe that goes to the cylinder runs up into attic 1 (where the header tank is) and then back down to the cylinder. There is an expansion pipe next to the cyclinder and a vent which returns water back into the header tank. I have often seen water spluttering out of this vent when the water is hot.
The secondary system runs from the cylinder to different points in the house, all of which seem to work OK except for the new kitchen. As far as I can make out there is no obvious vent, but there is a plastic pipe attached to something I can't get at the top of the cylinder which runs into a roofspace which could be a vent.
The new one I put in was simply an attempt to stop an air lock forming when the shower room tap was turned and didn't exist a few weeks ago. This was perhaps a lame idea but it was the best we could come up with at the time
Chrisr - the water never gets that hot, but the point you make could still be true.
wmyss - we do have two separate systems, my explanation is obviously not very good and I will try and explain in more detail. The primary system takes water directly from the borehole to the boiler (no tank! - which I believe would be more normal). Pipes from the boiler than run through the radiators and also through the coil in the cylinder (thanks for giving me the correct terminolgy) and back to the boiler. The boiler is situated in an outhouse and the pipe that goes to the cylinder runs up into attic 1 (where the header tank is) and then back down to the cylinder. There is an expansion pipe next to the cyclinder and a vent which returns water back into the header tank. I have often seen water spluttering out of this vent when the water is hot.
The secondary system runs from the cylinder to different points in the house, all of which seem to work OK except for the new kitchen. As far as I can make out there is no obvious vent, but there is a plastic pipe attached to something I can't get at the top of the cylinder which runs into a roofspace which could be a vent.
The new one I put in was simply an attempt to stop an air lock forming when the shower room tap was turned and didn't exist a few weeks ago. This was perhaps a lame idea but it was the best we could come up with at the time
Ian, Very interesting and must admit defeat and say I’ve never seen anything quite like the system you describe. And considering I started my apprenticeship in 1953 and long retired I never saw anything even similar.
Your boiler fed directly from a borehole. Well I suppose it must have pressure to lift into your property so to supply directly to a boiler would mean you have to have a pressure vessel which is the pre requisite to allow expansion. I have worked on these in industrial heating systems and they are quite unlike what you describe.
Was it installed by professionals Ian ??? With respect Ian I suspect that whilst you are describing what you see its not quite like this in reality.
To perhaps help in what you should be seeing is a cylinder with a flow and return on one side. Usually one inch bsp threads and in a direct line one above the other. These connections are the ends of the coil and will normally connect back to your boiler.
On the other side you have one (sometimes two) connections. This is smaller and takes a cold feed from a tank above it as a supply for your DHW.
On the top of the cylinder is another connection. This is the DHW supply to your taps. Also usually immediately the pipe leaves this connection a tee is fitted and this is the expansion/vent pipe which terminates in a bend over the top of your DHW tank. This serves both as a vent for air to escape and also as an expansion pipe to allow the heated DHW to expand.
This above is known as a indirect cylinder and the coil is an heat exchanger transferring heat through the walls of the coil to the secondary water. This type of cylinder has been the mainstay during my time apart from one which may have now gone out of existence, which was called a Primatic cylinder which also kept the primary and secondary systems apart but only used one tank and this was done by a air bubble preventing the waters from mixing.
With this type there would only be one expansion pipe and one tank. Maybe you could have one of these fitted?. It would be difficult for you to tell if it was a Primatic apart from having a label on.
I remember many years ago a Plumber coming to ask me to have a look at a house in which he was fitting a new cylinder. His problem was that he was getting no water to the boiler. It was quickly apparent that what he was doing was fitting a indirect cylinder as a replacement for a direct cylinder so anyone can get mixed up. I hope someone else can offer you something better Ian and would be interested to hear it.
wemyss
Your boiler fed directly from a borehole. Well I suppose it must have pressure to lift into your property so to supply directly to a boiler would mean you have to have a pressure vessel which is the pre requisite to allow expansion. I have worked on these in industrial heating systems and they are quite unlike what you describe.
Was it installed by professionals Ian ??? With respect Ian I suspect that whilst you are describing what you see its not quite like this in reality.
To perhaps help in what you should be seeing is a cylinder with a flow and return on one side. Usually one inch bsp threads and in a direct line one above the other. These connections are the ends of the coil and will normally connect back to your boiler.
On the other side you have one (sometimes two) connections. This is smaller and takes a cold feed from a tank above it as a supply for your DHW.
On the top of the cylinder is another connection. This is the DHW supply to your taps. Also usually immediately the pipe leaves this connection a tee is fitted and this is the expansion/vent pipe which terminates in a bend over the top of your DHW tank. This serves both as a vent for air to escape and also as an expansion pipe to allow the heated DHW to expand.
This above is known as a indirect cylinder and the coil is an heat exchanger transferring heat through the walls of the coil to the secondary water. This type of cylinder has been the mainstay during my time apart from one which may have now gone out of existence, which was called a Primatic cylinder which also kept the primary and secondary systems apart but only used one tank and this was done by a air bubble preventing the waters from mixing.
With this type there would only be one expansion pipe and one tank. Maybe you could have one of these fitted?. It would be difficult for you to tell if it was a Primatic apart from having a label on.
I remember many years ago a Plumber coming to ask me to have a look at a house in which he was fitting a new cylinder. His problem was that he was getting no water to the boiler. It was quickly apparent that what he was doing was fitting a indirect cylinder as a replacement for a direct cylinder so anyone can get mixed up. I hope someone else can offer you something better Ian and would be interested to hear it.
wemyss
wemyss, I very much appreciate the time spent trying to help me. When we bought the house 3 years ago the surveyor thought we were mad (and we probably were) as there were (and still are) lots of problems. Actually the plumbing is pretty good compared to the electrics!
I might have to live with the current setup until we get the next phase of the project done (by professionals) as this will move the cylinder anyway and it'll become their problem
As far as I can make out what we have is not dissimilar to what you describe, (although I can't easily get above the cylinder to work out exactly what's going on there) the complication has only come about with us extending the old pipework to a new kitchen.
Going back to the original problem though I can't get away from the thought that turning on the tap in the shower room (which works fine) draws down water and small amounts of air from the kitchen tap and pipework as this runs about an inch above the new T junction.
Anyway thanks all for the help
I might have to live with the current setup until we get the next phase of the project done (by professionals) as this will move the cylinder anyway and it'll become their problem
As far as I can make out what we have is not dissimilar to what you describe, (although I can't easily get above the cylinder to work out exactly what's going on there) the complication has only come about with us extending the old pipework to a new kitchen.
Going back to the original problem though I can't get away from the thought that turning on the tap in the shower room (which works fine) draws down water and small amounts of air from the kitchen tap and pipework as this runs about an inch above the new T junction.
Anyway thanks all for the help
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i think you have a hole in the coil inside the cylinder.
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