Domestic water tank cleaning - gone wrong!

macadamia_2

Hello, We renovated our house nearly 10 years ago and the plumber said that due to poor water pressure we needed a water tank in the loft. There was an old one there but we replaced it.  This tank supplies all our water - bar drinking water.

Last year I noticed a discharge in the water and on looking inside the tank we could see what looked like mould.  

We contacted "Water Quality Engineers" who typically (and by law) clean out commercial premises and they came and cleared our system and disinfected it all.  They said that the issue had probably been caused by the water heating in the loft and not moving during the summer.  We were away for several weeks during a very hot spell.  They cleaned the tank in November 2023.

In February this year I have noticed the discharge again.

I have contacted the company who just aren't interested in revisiting and tell me "water tank is likely to be predisposed to the formation of mould and this is not unusual." 

Does anyone have knowledge of this situation and what we should do next?  We paid circa £700 for this service which obviously didn't work.

pinkshoes

What were the T&Cs/warranty that came with the water tank? It's nearly 10 years old...

What were the guarantees that the water quality engineers offered with the service? Their job was to clean the tank out which they did.

Have you looked up details about that specific water tank to find out if anyone else has had mould issues?

It does sound odd that the tank was fine for 10 years but is now getting mould, so sounds to me it could be to do with the tank and not the service that they carried out. 

born_again

Is the tank covered up to stop the usual rubbish that drops down from inside of roof?

Aylesbury_Duck

I agree with others.  Something's changed.  Nothing can go wrong with a tank other than a leak, and it's not that.  It's something in your loft that's polluting the water.  Emptying the tank and treating the pipes will have solved the immediate problem, but something's caused it to reoccur.  Is the tank covered?  Have you got pests in the loft?  Any missing tiles or gaps where a bird, squirrel, etc could have got in, got thirsty and, well...

macadamia_2

Getting back to you...thanks for your thoughts.  The tank is covered.  The water comes from Thames Water (!)  I believe what they told me ie that the water would go off if left without any movement when it's very hot ( I can see condensation on the lid of the tank) and we do tend to go off in our camper over summer months for 4/5 weeks, so I wasn't 100pc shocked initially.

I can't find anyone else who has a water tank in their loft and I don't think a lot of people would have noticed the discharge (my husband didn't!)  When we looked in the tank we were horrified and we actually had the water tested (by another company) for Legionnaires. 

The fact that this has happened again after less than 5 pretty cold months has worried me.

Do any of you have water tanks? 

m0bov

Maybe drain down the water before you go away? Turn off the stop c*c* and run the taps from the tank side until it empties.

macadamia_2

m0bov said:

Maybe drain down the water before you go away? Turn off the stop c*c* and run the taps from the tank side until it empties.

Yes. I know that. This is not the current issue.

Aylesbury_Duck

macadamia_2 said:

Getting back to you...thanks for your thoughts.  The tank is covered.  The water comes from Thames Water (!)  I believe what they told me ie that the water would go off if left without any movement when it's very hot ( I can see condensation on the lid of the tank) and we do tend to go off in our camper over summer months for 4/5 weeks, so I wasn't 100pc shocked initially.

I can't find anyone else who has a water tank in their loft and I don't think a lot of people would have noticed the discharge (my husband didn't!)  When we looked in the tank we were horrified and we actually had the water tested (by another company) for Legionnaires. 

The fact that this has happened again after less than 5 pretty cold months has worried me.

Do any of you have water tanks? 

Well, it's one of two things.  Either something's getting into the tank and polluting the water, or the supply itself is polluted.  

I've never had a house without a tank - all five homes I've lived in had a tanked supply.  There's often condensation on the underside of the lid, it's perfectly normal as the water evaporates in a warm loft and condenses on the underside of the lid.  There's also normally visible stuff on the surface, not much of it but it is there.  All of the supply feeds that run from the tank are near the bottom, so any dust, etc. on the surface isn't a problem.

cannugec5

Until last August we had a cold water tank in the loft. The lid was ill  fitting and we occasionally had “debris”  come through the taps. At times this included blobs of, what I believed to be, mould. I would clear this by running the taps for a while. 

Whenever we had reason to be in the loft we would replace the lid - no idea how it actually moved! 

But when our ASHP was installed last summer they assured us the loft tank was no longer necessary and I was very glad to see the back of it. 

Our mains pressure is perfectly good without it.