Hot Water in Feed and Expansion Tank

[Hallucyn8]

Hi

Looking for a bit of advice, I've had a look through the FAQs and other posts and haven't managed to find my specific situation but apologies if this has been covered elsewhere.

For a little while now one of the overflow pipes coming from out of my loft has been dripping intermittently. It appears to be a regular, probably daily, occurrence but not in any great quantity as I've only ever actually witnessed a drip once or twice but the evidence is there as under the overflow pipe is a piece of wood that almost always has a damp patch.

I finally got round to going into the loft to investigate expecting to come across a an issue with a ball valve but found that the levels in both the hot water tank and F&E tank were below the overflow pipes and while the hot water tank valve does drip for a time after filling it does fully cut off before reaching the overflow.

Looking at the location of the two overflow pipes it appears that the dripping is coming from the F&E tank. It just so happens that while I was up there investigating the boiler was currently heating the hot water and there was a constant flow of hot water from what I believe is the vent pipe. It wasn't gushing out but was definitely a constant flow while the pump was running. I got the wife to turn off the hot water while I was up there and the flow immediately stopped. Despite this flow of water into the tank the water level was still nowhere near the overflow pipe and it doesn't look the tank is overflowing in the traditional sense. My best guess is that condensation may be building up in the overflow pipe and that is what is dripping outside. I haven't been up there while the central heating is on so can't currently comment as to whether the same thing is happening.

So really I have two questions:

1. Is the flow of hot water coming out of the pipe while the water is heating normal?
2. Does it sound feasible that the dripping is condensation rather than a genuine overflow?

And I guess the follow up would be if it's not normal what's the likely cause and the fix?

Thanks in advance for your help and hopefully my explanation and terminology is correct.

 

[PrenticeBoyofDerry]

When has the last time the system was cleaned/flushed out? It is possible that you have a blockage in the system.

 

[Hallucyn8]

Good question, it's not something that I've ever had done and I bought the house about 10 years ago. Is that something I could do myself or am I better off getting a professional in?

 

[JohnD]

you can try giving it a DIY chemical clean with X400 or similar. You leave the chemical circulating in normal use while it loosens sediment, then after a few weeks you drain and rinse to remove whatever has been loosened.

It may possibly do the trick, if not you are back where you started. But it only costs about £15 for the chemical plus some minutes of your time, so you might consider it worth a try, if you are willing to climb into the loft and willing to drain the system later using the drain cock and a hose.

A professional clean will cost you some hundreds of pounds.

If you can lay your hands on a strong magnet, hold it against the copper pipes where the 15mm F&E pipe from the loft joins the larger circulating pipes, probably in the airing cupboard. The black sediment is Magnetite, which will attract a magnet. The blockage is very likely here. Unfortunately it often forms a hard deposit due to mixing with limescale, and has to be cut out. A photo of the T joint may tell us more. If you can do DIY plumbing you could cut it out and replace.

All the time the system is overpumping like that it is drawing more dissolved air into the water, which will accelerate corrosion, so don't ignore it. It may reduce if you turn down the pump speed pending resolution.

 

[45yearsagasman]

View media item 55283Very good advice from JD. This may help to identify your pipework connections.

 

[Hallucyn8]

Thanks for the advice and the diagram. I've never drained a system before but it doesn't seem like it would be too much hassle so will look to give it a go. With regards to draining the system am I right in thinking I would want to drain from the drain cock that is just above the boiler and also from the one on the ground floor radiator?

 

[rules&rulers]

As mentioned,clean the system and add inhibitor.

It may not stop the symptoms you describe but at least the water will be clean/treated.

 

[JohnD]

the drain cock that is just above the boiler and also from the one on the ground floor radiator?

start with the ground floor one. try any others after that has stopped running.

 

[PrenticeBoyofDerry]

As it is F&E, you can start draining the system until the water runs clear, thereis no need to isolate the water supply to begin with. I would drain till clear, then isolate water, then introduce chemical cleaner and refill and vent.

Drain down from the lowest point/points on the system, there maybe more than one, depending on how the pipework is routed.

 

[dilalio]

Also Be aware that when draining the system through drain cocks and a hose, if the system water is in very bad condition (jet black is usually a sign) then your draining path could become blocked as deposits bottleneck towards the outlet you are opening up. Hence leaving the f&e running as @PrenticeBoyofDerry advised is a good idea to try and keep the flow and deposits in suspension.

 

[dibby90]

also clean your f and e tank out, could be a build up in the bottom of it and you don't want to drag any back into the system

 

[Hallucyn8]

Thanks for all the advice guys all very helpful. Will be putting it into practice asap

 

[PrenticeBoyofDerry]

also clean your f and e tank out, could be a build up in the bottom of it and you don't want to drag any back into the system

Good point, the sludge in the F&E is best cleaned before draining commences.

 

[Hallucyn8]

Thought I would report back after following all of your advice. It was all relatively straight forward although I did encounter a few issues.

First of all I cleaned out the F&E tank, I bailed the water out into a bucket and it was very sludgy, an orangey brown colour, but managed to get most of it out so that when it refilled I could actually see the bottom of the tank.

Next I went round opening all the radiator valves fully which is where I encountered the first issue(s). Two of the valves started leaking from the spindle before they were full opened so I had to leave these partially closed. I'm guessing this means that they need replacing but could it be a symptom of corrosion in the system?

I then started draining from the first of the drain cocks on the kitchen radiator with the feed running and was surprised to find that the water ran clear pretty much immediately. I then repeated this with the drain cock on the radiator in the hall way. This did run black for a while and then cleared. I then tried the drain cock above the boiler (return feed I think) and came across the second issue. First of all after opening the spindle nothing happened at all so I closed it, checked there were no kinks in the hose and tried again. This time I got a small amount of flow through the hose but an equal amount leaking out from the spindle itself. Again I'm guessing this means that the drain cock needs replacing and so I had to abandon flushing through here.

Next I stopped the feed into the F&E and drained the system starting from the same drain cock, initially the water was clear but became blacker as the process carried on. I opened the radiator bleed valves upstairs once the water level had dropped and once the water stopped flowing drained from the second radiator. I only got a small amount of water from this drain cock but ran into the final issue which was that the radiator in the lounge did seem to want to drain at all. Every time I opened the bleed valve I was getting water out immediately. The F&E tank had also not drained completely but I'm not sure whether this is to be expected or not.

Deciding that this was a good as I was going to get I shut all the drain cocks and bleed valves and opened the feed into the F&E tank and added the X400. Once it had finished filling I bled all the radiators and the valve above the diverter switch for hot water/radiators. There was a lot of air to let out but once done I started up both the hot water and heating and let the system get up to temperature. All seemed ok except for two cold radiators (the two with the drain cocks) so I shut off the system and bled again but nothing much happening. Started just the central heating this time and after lots of gurgling from the pipes got all radiators hot, shut down and bled again getting a fair bit more air out.

Everything seems ok now so I will leave the X400 in for a few weeks and drain and see how it goes. I did notice that the expansion pipe was still expelling hot water but I didn't read too much into this as the X400 won't have done its thing yet.

If anyone has any feedback on anything I've mentioned I would appreciate it but other than that thanks again for the advice and sorry the essay!

 

[dilalio]

When heating is on and circulating, shut all rads except one and leave for 5-10mins, then open another rad and shut the previous opened one. Do this for all rads on the circuit which will concentrate the power of your pump through each rad - also give each rad a few bangs with a softened mallet while it's the one that's open - this'll help get any crud into suspension and moving round the circuit.
If the system is really clogged it may be worth repeating the whole process with another bottle of cleaner when done.