leak from cold water tank, any advice?

[Penners]

But why one each - wouldn't he share?

We had two lofts, silly.

Wow - his and hers lofts. There's posh!

 

[Lime]

I've seen and dismantled a lot of pipework in my time but I have never had a correctly-fitted soldered joint fail, either through vibration or freezing.
What I have seen are solder joints that have either not been heated at all (held together by flux) or poorly soldered joints either not heated enough, inadequately fluxed or the pipe not cleaned beforehand.
Examination of the pipe end should tell you what went wrong.

 

[c r]

Ah, I just wrote a reply, then got asked to log in again, and what I wrote has disappeared...groan. Annoyingly I have also lost my camera so cannot post a photo here. I've just seen what Lime has written, I will have a look at the pipe end tomorrow but my eye is pretty untrained!

So thanks Robgil. Your points are making sense to my situation. The failed joint is on the flow side of the f+e tank, or to be clear, is not on the feed between f+e tank and the CH. Am I correct to assume from what you have written that the effect of water hammer would be particularly felt on the feed to the CH? We certainly do have water hammer, and this has gone on for years and years and years... Although I notice the tanks are now plastic, the whole system was designed and installed in the late 60s. We are always being told how out of date it is, its just you know, it has never really given us major problems. tempting fate here...

On investigation this morning, when I re-attached the failed joint it was obvious (even to my eyes) that the joint would have been under strain. The only support for about 1.5-2 metres of pipe between the two tanks has been, ahem, a large box, halfway along its length, that it rests on (!). I would intend to make a wooden framework and clip this pipe to it, to give support to the joint.

I appreciate what you say, I certainly don't want to do a bodge, but would just be particularly convenient at this time of year if I can do it myself, what with one thing and another. Its abit like opening a can of worms, going up into the loft...I notice plastic compression fittings & pipe (wrapped in insulation) were installed in the loftspace to replace the old lead mains feed to the big primary cold tank, this was done about 4 years ago. Would you consider this ok practice, as presumably its under less pressure?

thanks again

 

[middi]

Compression joints.There is absolutely nothing wrong to carry out repairs in pipework on a DIY basis in mains water pressurised copper pipes. No special tools required, no expense in call out charge and repairs for plumbers and best of all the the repair is not of a temporary nature. This repair can be carried out to "live" pipes with no danger of ending up with flawed solder joint.

For speed and simplicity a lot of plumbers would happily carry out a repair as above.
Admittedly, where the slight restriction in the water flow is of importance as to where it is situated in the pipe system then a soldered joint may be of benefit.

It is usually not advisable to fit more than one compression fitting per gravity fed line as this may seriously restrict flow. Then again, it all depends on the intended use of the gravity fed line.
The main (and valid) reason why a " soldered" system is much better than a compression fittings installation is the cost of materials and restriction of flow.
Middi

 

[Flyfisher]

I've always understood that water hammer was caused in pressurised pipework when a tap or valve was closed. I find it hard to imagine how a gravity outlet pipe would suffer from water hammer.

Also, I'm sure I've read somewhere, or been told, that plastic tanks and/or loosely-fixed pipes can be a cause of water hammer. Something to do with the tank/pipes moving slightly when the ball-valve finally shuts off, which then causes the ball-valve to slightly open again, causing an oscillation and thus water hammer for a short while until the ball-valve is closed with enough forced by the rising water that it doesn't 'bounce' open. In such cases, as I understand things, it's possible to cure the water hammer by fixing the pipework to the ball-valve more rigidly and/or provide a bit more support to the sides of the plastic tank.

Does that make any sense to the more experienced plumbers out there?

 

[MdB]

You are right that the gravity fed section won't be the cause of water hammer, it could suffer from it though. As you correctly state, water hammer in the ball valve will cause the entire tank to shake. This would put stress on any joints connected to the tank and potentially cause them to fail as seen here.

In my limited opinion, the best cure for water hammer is a pressure reducing valve where the supply enters the building. We had dreadful hammer (and 6+ bar water pressure) and the pressure reducing valve sorted it straight away and only cost £25 to buy if I remember right.

 

[robgil]

The fault was in the feed to the f+e tank, this is on mains pressure. Water hammer is when the flow of water is suddenly shut off causing shock waves, this is not to be confused with the groaning noise you get from say a cistern float valve with too much pressure running through it , this is entirely different and can be fixed by reducing the pressure or fitting a new valve.
A compression coupling should not restrict the flow, they are usually full bore fittings. In all my years do8ing plumbing work i would never put in a compression fitting in favour of soldering it, they can leak, a properly soldered joint will be a much better long term solution.
It sounds like your plumbing is a bit heath robinson and not securely fixed, it would be an easy enough job to re-do the pipe work and fix it down.
For what ever reason that solder joint blew you really need to make sure it wont happen again some where else along the pipe work, it will have blew at its weakest point, repair this weak point and the second weakest point could become the next in line.
water pressure didnt cause this damage.

 

[philpjuk100]

We had bad water hammer at our previous house,the ball valve bouncing about and water squirting out of the valve,we closed the stop cock a bit which cut down the hammer a bit but really slowed the washing machine and dishwasher filling.I thought if I could damp the ball valve arm it would help so mounted a bit of plastic (a bit cut off an old number plate about 6" long) and mounted it in the water horizontally below the valve on a bracket made from a bit of flattened 15mm pipe fastened to the arm with a couple of "jubilee"clips,it worked great and was still there when we sold the house 15 years later! phil.

 

[Flyfisher]

That's my nomination for the 2010 Outstanding Deductive Ingenuity award. Brilliant!

 

[Feltwell]

I've heard of folks suspending a small container - a plastic paint kettle is ideal - with some holes drilled in the bottom below the arm of the ball valve, to work as a damper and help stop the arm "bouncing" in much the same way as Phil's idea.

 

[philpjuk100]

Yep that sounds as if it would work and its less trouble!phil.

 

[c r]

I think I've used the term 'water hammer' incorrectly earlier in this thread, in using it to also mean a loud knocking sound within the CH system, that usually happens a few minutes after my boiler is switched on. This has happened for years and years, without seemingly being too much of a problem, we always have taken it to be trapped air in the system being suddenly released as the water temp rises.

Anyway, I'm sorry for the confusion. I wasn't referring before to the knocking sound when a tap is shut off, that type of 'hammer'.

Thanks again for your replies everyone.

 

[Lime]

I think I've used the term 'water hammer' incorrectly earlier in this thread, in using it to also mean a loud knocking sound within the CH system, that usually happens a few minutes after my boiler is switched on. This has happened for years and years, without seemingly being too much of a problem, we always have taken it to be trapped air in the system being suddenly released as the water temp rises.

That alarms me.
Knocking or banging from within the boiler may mean that calcium deposits (fur) are so thick that a blockage may occur.
From my childhood (when safety and maintainance was nothing like today... in fact it was nothing) knocking from back boilers was a prelude to an explosion.
I have seen incorrectly plumbed boilers in my time installed so that the circulating water was not a totally enclosed system.
(i.e. the calcium contents built up caused by the addition of more and more tap water)

c r I hope that this is not the sort of knocking/banging you mean.

However I suspect you are referring to the clicking of the copper pipes on joists as they expand and move with the sudden flow of heated water through them.
That is common.
Ordinary "clanking" (physical knocking together) of pipes is not the same sort of problem either.

 

[Penners]

In all my years do8ing plumbing work i would never put in a compression fitting in favour of soldering it, they can leak, a properly soldered joint will be a much better long term solution.

Ah, but that's exactly the point, Rob. "In all your years..." demonstrates your experience (and thus skill) as a plumber. A solder joint is the best, cheapest solution provided it is properly made. But in inexperienced hands, it can quite easily go wrong.

If a compression joint leaks this can usually be resolved with a tweak from a spanner. If a solder joint leaks it's a whole b*gger's muddle, involving draining down, drying the pipes, unsoldering, resoldering and so on. And it's not unknown for a dodgy solder joint to be effective just long enough for you to declare the system dry, and then to spring a leak later.

 

[Penners]

I think I've used the term 'water hammer' incorrectly earlier in this thread, in using it to also mean a loud knocking sound within the CH system, that usually happens a few minutes after my boiler is switched on.

Are you sure that's water hammer, and not just an extreme version of the clicking and ticking that many CH systems get, as the pipes expand?

 

[c r]

Yes thats what I mean, I shouldn't have said 'water hammer' before, but certainly the noise is much louder than clicking or ticking- knocking or banging would be more accurate, its abit like a clap of thunder! It always startles any unsuspecting non-residents in the home, a good conversation opener...It comes from upstairs- i.e closer to the f+e tank, where the problem was, which is why I mentioned it before, but I don't think in my case that possible vibrations from this could have caused the joint break, as it was on the flow/inlet side to this tank- the other side of it.

thanks for the concern, and info, Lime. Its definitely not coming from the boiler- think that would be a concern...

 

[Penners]

Yes thats what I mean, I shouldn't have said 'water hammer' before, but certainly the noise is much louder than clicking or ticking- knocking or banging would be more accurate, its abit like a clap of thunder!

Hmmm - if it's that loud, it sounds like rather more than pipe expansion. Have you tried tracing it to its source, while it's going on? It would worth doing so, and putting your hand (gloved if necessary!) on the guilty pipe to see what it feels like. You'll probably be able to feel expansion ticking, but it won't amount to much. Water hammer, on the other hand, will probably cause the pipe to jump noticeably at the location of maximum noise.

 

[AMc]

FWIW and it aint worth much - our central heating system made a serious bang every morning when the old boiler went on - waking me early - a cardinal sin. I eventually tracked it down to a copper pipe feeding the bedroom radiator. The joists hadn't been notched enough and the copper pipe was straining against the floor board until there was enough force to move the pipe suddenly.
The solution was to increase the notch by a few millimetres and for good measure I wrapped them with silicone baking parchment where they crossed the joists to give a low friction surface. I also insulated the rest of the pipes thus losing less heat out through the walls under the floor.
Given the polish wear on the surface of the pipes it had been going on for a while and would eventually have caused them to give out I would imagine.

 

[Penners]

I wrapped them with silicone baking parchment

I've also used that solution to solve the noisy creaking that expanding pipes can make when they reside in holes or notches in timber. However I would recommend using drawing pins to keep the parchment in place. Sometimes the constant movement of the pipe as it expands and contracts can push loose parchment out of place.

 

[FamilyWiggs]

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