Any plumbers around?

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Mattievrs
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Any plumbers around?

Post by Mattievrs »

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Got an issue that I'm after just a little advice on!
Have a cold water tank and what I believe to be a header tank for the central heating?
The joists under and around the header tank are damp and wet, there are no leaks at all but it's only around the header tank area. I'm sure I've seen the header tank overflowing in the past out the overflow on the side of the house and the water was warm enough to produce steam on occasion. Its not overflowed for a while now and isn't blocked etc. I'm left scratching my head as to why the joists around it are wet and causing the ceiling in the bathroom to discolour. What causes it to overflow or potentially push warm or hot water back into the tank?

The set up is attached as a picture, the higher of the tanks is the cold water tank, the lower the header tank.
Also, there is a boiler in the utility room, a hot water cylinder in the airing cupboard and I don't run a combi boiler if that helps?
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axel_knutt
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Re: Any plumbers around?

Post by axel_knutt »

If the ball valve needs adjusting that would cause the header tank to overfill, then if there's excessive air in the radiators, the expansion of that as the system warms up might be enough to push too much water back up into the tank. Either way, any overflow should be going out of the pipe unless it's blocked, not on the loft floor.
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Mattievrs
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Re: Any plumbers around?

Post by Mattievrs »

axel_knutt wrote: 30 Jan 2023, 10:19pm If the ball valve needs adjusting that would cause the header tank to overfill, then if there's excessive air in the radiators, the expansion of that as the system warms up might be enough to push too much water back up into the tank. Either way, any overflow should be going out of the pipe unless it's blocked, not on the loft floor.
Thanks for the reply. Would it be feasible that the header is getting water warm enough to condense on the outside of the tank as the outside temp is lower and potentially make the condensate drip onto the surrounding joists?

It's only the joists that's wet and is leaving a mark on the roof and making the grout wet on the wall in the adjoining shower room.
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Cowsham
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Re: Any plumbers around?

Post by Cowsham »

Yes it's very possible the water in the tank is too hot due to a fault in the system and making water condense on the galvanized sides. ( most tanks are plastic now )

The bad news
One of 4 things could be heating the Feed & expansion ( or F&E or header ) tank

1 I'll start with the worst possible thing -- A coil leak in the hot water cylinder -- this is why the expansion tank is positioned below the main storage water tank. If there's a leak in the direct heating coil inside the cylinder the pressure of the main tank will push storage tank water into the heating circuit water via a hole in the cylinder coil sending water into the heating system and thus into the header tank where it escapes out the overflow. Better that way than the other way around hence the F&E tank below the main tank and not the other way round ie heating water with chemicals in getting into the indirect hot water cylinder.
This will be an expensive fix -- requires a new cylinder.

2 the next one is pumping over -- ie the pump or pipe work has been changed and sending water the wrong way around the system and it has nowhere else to go but up the vent into the tank -- you'll not have as much water coming out the overflow unless the ballcock is set too high ie water level too near the overflow and expansion of water pushes some out. -- just set the ballcock about a couple of inches from the outlet of the tank to the heating system. This picture from an old book of mine might explain why the position of the pump matters.
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The top right picture is the correct order of pump to pipes.

3 the pump speed has been set too high causing pump over

4 the ballcock is leaking when it's supposed to be shut but that would normally only cause water out the over flow -- tank would most likely be cold.

I'm not a plumber but have had to research all this recently due to a restoration project -- doing all the plumbing myself. I've been involved with engineering projects at work which involve thermodynamics of plumbing pipework etc but my discipline is mainly electronics.
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offroader
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Re: Any plumbers around?

Post by offroader »

Is there a vent pipe above the expansion tank?
If there is try loosely securing a plastic bag over the end of it. If this collects water then your system is pumping over as above.

A holed heating coil or leaky ballcock will make the overflow drip continuously, pump over or expansion will only cause issues when the boiler is on

Once you know where and when the water in the expansion tank is coming from the problem gets easier to diagnose
uwidavid
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Re: Any plumbers around?

Post by uwidavid »

The ballcock in the top-up/expansion tank gets very little use so it needs to be in good condition. Any slow drips will accumulate and eventually cause an overflow.
pete75
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Re: Any plumbers around?

Post by pete75 »

Had this happen at my house. After investigation found it was the coil in the hot water cylinder leaking. They have a finite lifespan. Happened about four years ago and cost just over £200 to replace cylinder. Got £35 for the old cylinder at a scrap yard , so really the cost was under £200.
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Cowsham
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Re: Any plumbers around?

Post by Cowsham »

pete75 wrote: 31 Jan 2023, 9:30am Had this happen at my house. After investigation found it was the coil in the hot water cylinder leaking. They have a finite lifespan. Happened about four years ago and cost just over £200 to replace cylinder. Got £35 for the old cylinder at a scrap yard , so really the cost was under £200.
Did you instal it yourself Pete ?
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pete75
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Re: Any plumbers around?

Post by pete75 »

Cowsham wrote: 31 Jan 2023, 10:05am
pete75 wrote: 31 Jan 2023, 9:30am Had this happen at my house. After investigation found it was the coil in the hot water cylinder leaking. They have a finite lifespan. Happened about four years ago and cost just over £200 to replace cylinder. Got £35 for the old cylinder at a scrap yard , so really the cost was under £200.
Did you instal it yourself Pete ?
Yes. It's only a couple of hours work. System and tank drain, four pipes to undo, one electrical connection if you have an immersion heater and reverse to fit. Longest part of the job is the draining. Screwfix had cylinders on offer at the time. I think they're about £300 now.
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Cowsham
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Re: Any plumbers around?

Post by Cowsham »

pete75 wrote: 31 Jan 2023, 10:42am
Cowsham wrote: 31 Jan 2023, 10:05am
pete75 wrote: 31 Jan 2023, 9:30am Had this happen at my house. After investigation found it was the coil in the hot water cylinder leaking. They have a finite lifespan. Happened about four years ago and cost just over £200 to replace cylinder. Got £35 for the old cylinder at a scrap yard , so really the cost was under £200.
Did you instal it yourself Pete ?
Yes. It's only a couple of hours work. System and tank drain, four pipes to undo, one electrical connection if you have an immersion heater and reverse to fit. Longest part of the job is the draining. Screwfix had cylinders on offer at the time. I think they're about £300 now.
That's if it's not custom made -- you can get it made to suit your particular needs or system with flanges where you need them. If you cant do the work yourself I'd say paying a plumber now is heavy money.
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pete75
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Re: Any plumbers around?

Post by pete75 »

Cowsham wrote: 31 Jan 2023, 10:53am
pete75 wrote: 31 Jan 2023, 10:42am
Cowsham wrote: 31 Jan 2023, 10:05am

Did you instal it yourself Pete ?
Yes. It's only a couple of hours work. System and tank drain, four pipes to undo, one electrical connection if you have an immersion heater and reverse to fit. Longest part of the job is the draining. Screwfix had cylinders on offer at the time. I think they're about £300 now.
That's if it's not custom made -- you can get it made to suit your particular needs or system with flanges where you need them. If you cant do the work yourself I'd say paying a plumber now is heavy money.
I think most people have have standard sized tanks. It's much quicker, easier and less costly to pipe the system to a standard tank than have a tank made, at some expense, to fit non standard pipe work.
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wheelyhappy99
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Re: Any plumbers around?

Post by wheelyhappy99 »

If the cylinder coil has failed there's an alternative solution which is to convert the system to mains pressure with a suitable new cylinder and pressure vessel. That will be more expensive but it's a more efficient heating setup, and you can take out the old tanks and pipework, so much less opportunity for condensation in future.
Mattievrs
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Re: Any plumbers around?

Post by Mattievrs »

Wow, thanks for all the replies so far.
So basically, the hot water cylinder is about 5 months old now, and since that was installed, it hasn't overflowed once. The pump and the valves on the boiler are around 2 years old, I think. Now I've been up in the loft, and the tank is definitely not overflowing, and the ballcock is fully submerged and over 2 days' worth of monitoring the level of water hasn't changed. The valve on the ballcock is also not leaking fro. What I can see and/or hear.
One thing worth noting here is that it's probably a good 5 degrees cooler in the loft than either of the bathrooms, and it seems that most of the insulation that covered the areas of the the bathrooms has been pulled up and left in a heap either side. Surely this can't be down to pure condensation can it? It's definitely wet around the area of the tank and the one joist is very wet which matches the marks on the ceiling. The tank is 100% not leaking either........
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Mattievrs
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Location: Leicester

Re: Any plumbers around?

Post by Mattievrs »

Right update!

I've been up there again with a proper torch and had a good look around. It's the tank that's leaking! Not obvious but managed to lie down along a joist and get a good look under the tank. The tank sits on 2 wooden pieces that go across the wet joist at right angles but if pushed they move slightly to reveal 2 long rusty parts where the tank is rotting through. Thankfully its no worse but I've definitely now seen a drip of rusty water and both shorter pieces of wood are also very wet too. Can't be ar53d to sort it so the plumber it is!
Thanks for all the replies to this post and hope it can be sorted quickly before it gets too bad. Cheers all.
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Cowsham
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Re: Any plumbers around?

Post by Cowsham »

Mattievrs wrote: 31 Jan 2023, 6:11pm Right update!

I've been up there again with a proper torch and had a good look around. It's the tank that's leaking! Not obvious but managed to lie down along a joist and get a good look under the tank. The tank sits on 2 wooden pieces that go across the wet joist at right angles but if pushed they move slightly to reveal 2 long rusty parts where the tank is rotting through. Thankfully its no worse but I've definitely now seen a drip of rusty water and both shorter pieces of wood are also very wet too. Can't be ar53d to sort it so the plumber it is!
Thanks for all the replies to this post and hope it can be sorted quickly before it gets too bad. Cheers all.
Phew! That's an easy fix -- buy a new plastic tank and I think 22mm and 40mm hole saw for your drill new ballcock new outlet tank flange and maybe a replace the old gate valve ( for isolating the outlet to heating system )

drill 22mm for ballcock and outlet flange and a 40mm hole for the overflow -- you might need to drill a hole in the lid for the vent pipe to drop in. You might also want to buy a bit of 15mm copper pipe and a couple of new olives ( you can use the old nuts or if they are chewed up new ones are cheap ) to extend the existing pipes to new tank.

You'll need to switch off the water supply and isolate the feed to the heating system ( of course you'll have to drain system down a bit if you want to replace the old gate valve -- I put ball valves on mine -- much better to use. ) but all that is fairly easy stuff to do yourself. If you can replace a derailer on a bike you'll have no problem doing this simple task.
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