CH system leaking under floor

[Porker]

Hi,

I posted an earler thread here related to a problem with my CH system and followed the advice. However, I think the problem is a little more serious and I would like the opinion of some of the regulars on here before I go chopping the system around.

Original issue was (and still is) air in the system causing major clanking and banging in the boiler. (Glow worm Ultimate 120FF open system). I assumed poor flow so flushed the system out. All started OK and then back to the old state. Very little muck came out and there don't appear to be any blockages.

Now, I have been away a couple of times over Xmas and away from the house for a few days at a time. What I have noticed is that on returning to the house after a few days, water is still being taken from the header tank! My summary - I must have a leak somewhere. Now there is no evidence of any leaks in the house in ceilings etc. and the amount of water taken must amount to a fair bit (10's of gallons a day). The only place I can think of that it must be escaping therefore is the hot water tank (leak in the coil - but no discoloured water or other evidence there) or into the ground where all the downstairs pipes run in the concrete floors - this is my bet. Pulling the floors up is not really an option as expensive tiles and wood were laid over the top eariler this year.

On reflection the CH has never worked well and maybe the problem has always been there. My plan is to replace all the pipework downstairs by running in the ceiling space overhead and renewing the rads at the same time. It is a major job but at least the upstairs is half ready with boards up etc. so it could be worse.

This weekend I plan to firstly confirm it is not the HW tank by draining the water out and seeing if it refills with CH water then isolate the downstairs CH system which is a pain as it is 28mm pipes fitted tight against a wall to confirm this is the problem as the system should not keep draing water if the leaking section is removed.

I have a few questions:

1/ Do you think my diagnosis is fair given what I have said? - I simply can't think of any other explanation. Is their any way of pressure testing a section and what gear would I need?
2/ If I go to the trouble of putting in a new system downstairs would you go to the trouble of putting in a seperate zone?
3/ Would you use plastic pipe as this would make routing a lot easier or would you use copper?
4/ What is a decent TRV to use as most of the ones I have come across in the past stick for a pastime?

 

[Agile]

It would have been better to continue the old thread.

If you think that you have air in the system then the last thing you should be thinking of is to drain it again!

At one point on the old string you said in passing that the original pump was blocked with "scale". No one questioned that but it was a very important clue to resolving the problem if we knew exactly what it was.

Is the level in the F&E tank still going down by 75 mm in a few seconds? That indicates a significant leak. Is there no sign of dampness anywhere?

Tony

 

[Porker]

Apologies for not continuing the old thread, I will in the future. The old pump had scale in the plastic impeller channels which I thought may hinder operation but this doesn't amount to a great deal so I discounted it as a minor thing. A blockage gives the impression that there was a significant amount of scale and there wasn't really.

The F&E tank looses around 3" of water in a few minutes I haven't timed it but I would say its enough to be a significant amout of loss.

No sign of dampness anywhere. My house is totally dry. Having dug up some of the floor in the past when I drilled through a 15mm pipe off the rising main, I would say that water could drain away without any noticeable dampness on the surface as uder the slab is fairly porous material.

There may well be a secondary issue but my thinking was that fixing the leak would be somewhere to start as this can't be helping and any inhibitor would quickly be diluted away.

 

[Agile]

Finding the "scale" ( probably oxide flakes actually but still a clue to the problem ) in the pump indicated two problems.

Firstly the "scale" indicates the system is probably quite badly sludged up and blockages are quite likely elsewhere.

Secondly and most relevant, even a very small amount of dirt in the impeller will very seriously affect the pumping efficiency. It seems to me that even if only half the flutes are blocked then there is only a very small pumping effect. In other words the practical effect seems to be more serious that it will look.

Its very difficult to find leaks under concrete. A specialist firm adds a smellable chemical and then detects the smell. A thermal imaging camera might show it. Even a simple IR detector can sometimes show it up if used with a little experience.

Tony

 

[Porker]

Tony, Thanks for the reply. I thought the same regarding the pumping efficiency with particles in the impellor. Rather than detect the leak in the floor which I think would be very difficult as I don't even know where they run, I would rather replace the whole of the piping for the ground floor by dropping down from above. I have never been happy with the arrangement of pipes in the floor and some of the protection I've seen for the pipes is iffy. I am also renovating the first floor now so the disruption will be less now than later. I have thought it through and the runs are not too tricky. I also want to replace the rads as they have sludge in them which doesn't budge with a power flush. The rad system is older than the current boiler. I don't mind the work but need to be sure that there is indeed a leak under the floor.

 

[bab]

I would say u must have a leak under the floor as a leak at that rate would overflow the lower tank . & if it aint the heating . if the lower tank is the heating then that would be the 1 over flowing & not dropping. Can u not bung the system & fit a couple of gate valves where the main circs for the ground floor drop to isolate the ground floor to prove the leak & stop any further corrosion to the system while repiping takes place. ya gona need all no rads soon if you dont stop all that oxygen injection into the system.

 

[Porker]

bab - That's exactly what I intend to do this weekend. A couple of 28mm valves. The difficult bit is that the pipes are tight against a wall and hard to get to without removing the pump etc. I was planning on cutting out a section and then using tees to stand the valvle off from the wall as there is no way the pipes can be eased apart to get the valve in.

I was also going to replace the rads anyway with new. I am considering using Hep2o for the routing under the floor as the house has been extended and messed about with and copper for the drops to the rads. never quite sure about plastic but everyone I know who has used it has had no problems.

 

[Agile]

It all depends on who you know!

I dont know the installers but I have been called to repair a lot of leaking plastic joints.

Tony

 

[Slugbabydotcom]

into the ground where all the downstairs pipes run in the concrete floors - this is my bet.

MINE TOO!

If theres a leak there's usually a clue to tell the tale.

Use your eyes and ears. Have a mooch about, move stuff and look for damp patches, listen for strange noises. One of these might be useful to help figure out where your pipes run. Spend at least £30 if you get one from that site then flog it on ebay if you have no use for it afterwards. Maplins and the likes sometimes do the laser one for about £25