Lockdown Flood

Discussion in 'Plumbers' Talk' started by Mattyuk, May 21, 2020.

  1. Mattyuk

    Mattyuk New Member

    Just back at my Mum's house after she's been away for a couple of weeks due to isolation, and found the hall ceiling on the hall floor when I walked in. Fantastic.

    Turns out the hot water (not the CH) had been left on 24/7. The cupboard with the (vented) hot water cylinder was flooded out with water dripping from the roof of the cupboard. Dripping water was tepid not cold, so it's not a leak from the cold water tank in the loft (also checked and no evidence of moisture up there).

    The tank is boxed in so I haven't been able to do full investigation yet, but my best guess is that the water in the tank has been boiling away for the last couple of weeks, and this is all steam condensing on the soffit and dripping down into the cupboard. All the towels and sheets are destroyed.

    Odd thing is, shouldn't the thermostat on the water tank (set to 40, oddly) signal to the boiler to shut off even if it is on 24/7 once the set temperature has been reached? And even if that fails, shouldn't the cylinder just vent into the feeder/overflow tank in the loft rather than spewing steam over the airing cupboard?

    I need to take the boxing apart and see what's happened, but I'd be grateful for any early thoughts on what might have happened here?

    We had a total cowboy in 15 years ago who I suspect has crossed the CH and the HW circuits, plus wonder if his controls have been bodged, but then it's run for 15 years ok on a timer, so lost on me!

    Any suggestions gratefully appreciated so I can know what to have a look at.

    Could the thermostat have failed and the vent pipe be blocked/installed incorrectly? But even then how the hell would steam (assuming that's what it was) be getting out of the HW cylinder? Do they have some sort of emergency pressure release valve?

    Ah the joys. Spending the day putting the ceiling back up before Mum comes back to find it all in pieces. :(
  2. Joe the Plumber

    Joe the Plumber Screwfix Select

    Before you put it back yourself, don't forget this is exactly what you have house insurance for. Get them onto it, you pay them enough.
    sparky steve likes this.
  3. sparky steve

    sparky steve Active Member

    Also your hot water temp set at 40 is too low, should be set at 60 to prevent bacteria growth (legionella)
    Joe the Plumber and Creek like this.
  4. Mike58

    Mike58 Screwfix Select

    Do the basics to secure the property and make it safe - water off, boiler off. And if there is a chance it has become wet, power too.

    Then call the insurance company, do not mention "cowboy" just that it has been OK for 15 years. Do not give any reason for them to escape their liabilities.

    Don't reinstate the ceiling for three reasons, one they need to see it, two, you need to ensure it is fully dried out, three the insurance company should pay.
    Joe the Plumber likes this.
  5. Mattyuk

    Mattyuk New Member

    Thanks for this. I'm aware of the legionella issue, but good shout (not sure who put it at 40 - I left it at 60+).

    To be honest I'm pretty handy so can repair the damage to the ceiling for way less than the insurance excess - I'm just trying to get an early heads up on what might have happened with the cylinder - is there a safety net that has failed?

    I'll speak to the insurers though and see what their process is. I'm already irritated with them though for overcharging my elderly mother by about three times the odds, then refusing to pay when the house supply sprung a leak under the driveway as it was "natural wear and tear". Jokers.
  6. Mattyuk

    Mattyuk New Member

    Update following some investigation.

    Thermostat and controls seem to be working fine - heats up the water to the set temperature then turns the boiler off.

    No odd water connections that I can see so far - standard indirect vented system with a three port valve. TPV working fine in all three positions and responds fine to the programmer.

    I'm running the hot water water up overnight to see if it's wet again in the morning.

    So I'm lost. The only thing I did notice was then when I went to look at the programmer (ie. the timer/controller unit) earlier on, it had no power but I'm 90% sure it was switched on at the wall. So possibly a loose connection to the programmer?

    Could that cause the cylinder to overheat? But again shouldn't the steam have just vented into the loft above via the secondary vent pipe?

    So confused...
  7. Joe the Plumber

    Joe the Plumber Screwfix Select

    Just a thought. If the cold loft tank is near the cupboard, have a look and see if the water level has been up at the overflow. If the overflow fitting's been leaking,
    that could have been dripping down into the cupboard as, with no one in the house for two weeks using hot water, the tank will have been constantly full.

    Given how hot it's been, it's possible it could have dried out in the roof but still been wet in the cupboard, and that could also account for the water on the ceiling being tepid
    (heat from the roof).

    Sorry if you've already done all this, but I thought I'd mention it.
    WillyEckerslike and sparky steve like this.
  8. Mattyuk

    Mattyuk New Member

    Joe this is genius I like the way you're thinking even if that isn't what has happened.

    Have had a quick look in the cold water tank and it's not overflowing at the moment (although I've been using water for the last couple days), but the level of the water is super high - higher than the cutoff point for the float valve, so somethings definitely been discharging waste water into it.

    I'll try to check if the overflow is leaking today. Just so I understand the logic though, in theory the hot water cylinder would have been full, and turning on and off automatically for a couple of weeks via the cylinder themostate (set to 40). Would the expansion of this water up and down around 40 degrees be enough to keep spitting vent water into the cold water tank? Is that what you think might have been happening? Or would the controls/thermostat have to failed to create enough expansion to fill the cold water tank up?

    Sorry just trying to make sure i've understood the logic - it's interesting stuff.
  9. Mattyuk

    Mattyuk New Member

    Another update - the overflow from the cold water tank is blocked. So best guess is the cold water storage tank has overflowed. As you say, there's no evidence of water around the tank, but it's damp underneath, so I think the whole tank has overflowed over the sides of the tank. As you say I guess the hot weather has dried out the loft, but not underneath the tank.

    So that looks to be the cause, but Joe could you explain the logic - see my previous post about expansion of water/discharge into the cold water tank. I'm trying to work out why that has happened whilst we were away from the house with the hot water on.
    Joe the Plumber likes this.
  10. Joe the Plumber

    Joe the Plumber Screwfix Select

    Great stuff Matty. It's probably as simple as the ball valve is slowly dripping into the tank, it wouldn't take much over two weeks to over fill it, and the water's leaking out from either the overflow pipe or fitting, or the hole where the ball valve goes through the tank. Or coming over the top as you suggested.

    A new ball valve, unblock the overflow pipe (and test it!), sort out where exactly it's leaked from, fix the leak (if applicable) and you're done.

    Apart from the ceiling....

    I think you're probably safe to forget the hot cylinder as a cause, but please double check it of course.
    Last edited: May 22, 2020
  11. Mattyuk

    Mattyuk New Member

    First prize to Joe.

    Turns out both the overflow pipe was blocked AND it was leaking at the fitting where it joined the tank which was inexplicably loose quite a few turns. TIghtened up but still dripping a bit so it's off to find a new one.
    Thanks a million Joe - you made it a lot less painful to find the source (which was of course in the least possibly accessible place).

    Incidentally the overflow pipe doesn't look to have enough of a head on it vs its outlet on the tank - it really dribbles out when I was testing it. If the ball valve failed open (I guess unlikely but you never know), the tank would definitely fill faster than the overflow drained out ie. flood. Am I right in thinking that's not ideal but not a building regs fail as the overflow is meant to serve as an early visual warning rather than being able to drain at the same rate as the tank could possibly fill if the ball valve failed open?

    Sorry for all the questions - just find this stuff fascinating. I am veeeery close to training to be a plumber.

    Also guess what is an exclusion on our household insurance policy - "leaking overflows". Classic.
  12. Joe the Plumber

    Joe the Plumber Screwfix Select

    I think I'd be inclined to re-work the overflow so that it's better able to cope with the full flow of the ball valve. It certainly ought to be able to.

    You could even fit a second overflow if it's still a worry.

    Don't forget to change the ball valve too. That's where the water probably came from.

    Anyhow, I'm glad you've got to the bottom of it. Thanks for letting us know.
    Mattyuk likes this.
  13. Mattyuk

    Mattyuk New Member

    He's too good (or she if Joe is a pseudonym). Leaking ball valve. Leaking overflow. Blocked overflow. A triple whammy.
    Well done and thanks, Joe. If there was a way to buy you a virtual pint I would.
    Joe the Plumber likes this.
  14. Joe the Plumber

    Joe the Plumber Screwfix Select

    Thanks Matty. I am a plumber, a bloke, and my name is Joe! I'm glad to have been able to help.
  15. Mattyuk

    Mattyuk New Member

    ...aaand the supply stopcock to the tank feed is seized. Man... Ball valve and stopcock replaced, new rubber washer put on overflow fitting and now is holding the seal again. Phew.

    Anyway that just leaves one last question. I've cleaned the bug screen in the overflow pipe and it's not improved the flow. So the overflow is definitely not man enough to handle a fully failed open ball valve.

    Is head (ie. the difference in height between the overflow and the outlet) and pipe diameter the only two factors I have to play with here? At the moment the head is about 15cm at a guess, the pipe is 15mm and there is obviously a dogleg to get it out through the wall. Pretty sure it should be a 19mm min pipe, but is there a recommended head?

    Thanks all/anyone for the advice. Got there in the end.
  16. Mattyuk

    Mattyuk New Member

    Stand corrected, Cig packet says the pipe is 19mm+, but the fall is probably nearer 10cm!
    Sorry can't work out how to edit previous posts!
  17. Joe the Plumber

    Joe the Plumber Screwfix Select

    The fall will be okay. Some only have about an inch. Not being funny, are you sure the whole pipe is completely unblocked now?
  18. Mattyuk

    Mattyuk New Member

    yes 95% sure. it looks to me like it might be rising a bit as it passes through the wall too, so the head might be even less. also it kind of glugs (stops and starts) when it's running like the water is getting stuck with an air trap somewhere...

    Think I might just run a new one...

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