Cleaning your water tank in loft

[Arapawa]

I didn't know this was a thing. First house that we've had a tank for hot water.

Who has done this and how did you do it?

I've never done this. Never heard about it either.

Nope. Never heard of this. Is it really a thing?

Are they not cold water feeder tanks in the loft and then a hot water cylinder elsewhere?

Who says you need to clean them?

We get cold directly from the mains but our hot water tank is in the loft. We put a new one in when we moved in 7 years ago.

I've noticed staining around the plug hole and overflow hole...kind of black and I've just googled and yes it's a thing!

I imagine water sits there in a tank in the heat and there could be things growing in it. There is loads of info on google.

Are you sure you mean hot water? Not a cold water loft tank (that may fill your hot water immersion tank/heater)? Is it a sealed vessel or a tank you can get at the inside of?

I cleaned the cold tank when we moved into a new house, purely because the house had been empty a long time (with the tank full) and I was worried about legionella.

I just turned the water off at main stop cock, and turned the cold bath tap on until it ran dry, then wiped out the mildewy gak on the inside of the tank. Turned the stop tap on again for 30 seconds or so, and off again, and rinsed out the residual gak via the bath tap, then turned off the bath tap and turned on the stop tap and let it fill up.

If you mean clean inside the immersion / tank that holds hot water - you don't need to, it's hot enough to kill any bugs.

I've noticed staining around the plug hole and overflow hole...kind of black and I've just googled and yes it's a thing!

Might be simpler to clean those things rather than your hot water tank tbh. Hot water tanks are normally heated to 55-60° to prevent bacterial growth. And black around a sink is probably mold from damp rather than a hot water tank.

Is it not a cylinder rather than a tank?
Surely the hot water kills bacteria if its the hot water cylinder

Is it not just mould or mildew at the sink that needs cleaning?

Black gunk in your overflow or the plughole doesn't come from the tank. It grows in situ. Just clean it with soda or bleach. You do not need to clean your tank or immersion.

Do you mean black around the outlet and over flow on the tank? You can't see inside a hot water tank, it's sealed.

What does the tank look like and what is it made of? If it's plastic (you said it's new 7 yrs ago - old ones might be galvanised metal) with a lid you lift off, there should not be hot water in it.

It's not mould. There's a cap that covers the overflow and when I take that out to clean it I can see it's blank and gunky. I've never seen this before. Am SW London - so not the best water.

Ok, I just checked. It's a storage tank with a lid. Cold water goes in there and is stored and then it's used for hot water for all domestic use. We do have a water softener.

Our drinking cold water doesn't go near the tank. It's directly from the mains.

OP, can you post a pic of the tank please?

I'm concerned that if you have a tank containing hot water in your loft, that you can access the inside of, that you may have a vented immersion backfilling into a cold header tank.

@pigletjohn is probably the best person to advise.

OK, good, and the water in there is not hot?

Do you have any taps that also run off that tank - not drinking water, so bath taps / mixer shower (not electric) / toilet cisterns?

Your tank will be sealed with a lid?
cleaning it isnt a thing

the black mould is something else and a sod to get rid of

We used to have a tank like that in an old house and never thought much of it until the water in the bathroom had a funny smell. DH went up to investigate and found the lid had shifted and a starling had drowned and was rotting in the water. It was disgusting.

Shortly after, we were getting work done and got rid of the tank and had all the water coming straight from the mains.

Sounds like a cold water feeder tank that feeds your central heating system. It may also feed your upstairs taps. You likely have a hot water cylinder somewhere else (in a cupboard maybe) that feeds your hot water taps.

The water in the tank isn't hot but it is all used for our showering, and everywhere else hot non potable water is used in the house.

Our cold water for drinking comes the mains and doesn't go near that tank

Sounds like mould and gunk to me. Nothing to do with your tanks/cylinders

OK, that's perfectly normal.

If you want to clean the tank, which is entirely up to you, you need to turn of the water supply to the tank so it doesn't keep filling, and then drain the tank via a cold bath tap / flushing the loo.

You can figure out which cold taps etc come from the tank, by turning off your main stop cock, and running the cold tap and seeing if the water stops (directly from the mains) or keeps running (from the tank). The cold tank probably holds about a bath full of water, it's not a huge amount you'll be wasting.

Then you need to get in the loft and scrub the inside of the tank / the overflow / anything else that looks grubby. You'll probably now have a small amount of murky water in the bottom of the tank. You can mop that out with old towels or push it out the outlet to come out of the bath tap.

Have someone turn on the main stop cock for a little while so some water comes into the tank, use it to rinse around any dregs and flush that out the outlet to come out of your bath tap and if there's any remaining mop it out with an old towel.

Turn off the bath tap, turn on the main stop cock, put the lid on the tank. Finished.

To add - I definitely wouldn't drain the tank via anything that heats water (electric shower / hot taps) as you don't want to run them dry and damage them, or get the resulting murky water from scrubbing into them.