Brown water from hot water cylinder

[JJJ]

My hot water has gone a shade of brown. The cold water from the cold tank is clear.

What would cause this?

TIA

Jim

[The Natural Philosopher]

Dead bird in the cold water tank that has now rotted away completely?

[Andy]

Your primatic cylinder has lost its air bubble. You can check if its a primatic cylinder by the fact the flow and return from the cylinder do not have a vent or feed pipe.

[TheScullster]

If it's an indirect cylinder (one that has an internal coil for water heating from the boiler/central heating circuit) then maybe the coil has failed! This will allow water from the heating circuit, radiator sludge etc, into your hot water. If your central heating system is open vented type (with small water "header" tank in loft) check to see if there are signs of water leaving that small tank eg slowly dripping float valve.

Phil

[JJJ]

It's a pressurised closed heating circuit.

It had a bit of a slow leak anyway, so have been losing pressure. How can I prove it's getting into the HW via the indirect coil? (other than the brown colour of course..)

Jim

[Christian McArdle]

The combination of the two factors makes it very likely.

You could remove the connections to the indirect coil and do a pressure test (it just needs a pressure gauge, a pump and various connectors/stop ends to piece something together).

Christian.

[TheScullster]

Presumably water would leak from the cylinder into the coil if you disconnected the coil!

Phil

[Christian McArdle]

Certainly if the leak is severe. However, the leaks are often pinhole types that only pass significant amounts of water when there is a good pressure difference, such as between the high pressure primary circuit and the almost zero pressure (in comparison) hot water.

It would be difficult to use as a diagnostic method unless the leak was particularly severe, as it will drip for ages anyway.

Christian.

[JJJ]

Well, just to complicate things further... it's gone clear again!

The water was particularly scalding this morning (haven't gotten around to fitting a cylinder thermostat yet..). Could the extreme temperature just have stirred up gunk in the bottom of the HW cylinder through convection??

Either that, or maybe the water company was working on the supply and it obviously would take longer to work its way out of the hot water circuit...

I'll reserve judgement for a couple of days before doing anything radical methinks...

Jim

[doozer]

Funny, we get almost exactly the same problem with our sealed system. After the water has been on (especially if it accidentally gets put on a couple of times) and it's really good and hot the first bit of hot water is brown (I've only noticed it from one tap though). If we draw just a little water while it's heating it doesn't happen.

I've not been able to figure out what is happening and it doesn't happen every time. I spoke to a plumber that reckoned it was probably just a bit of dirt getting kicked up. I considered that it might be a leak in the heating coil but we don't lose noticeable pressure on the sealed circuit over times scales of less than a year so if there was a leak it would have to be microscopic so couldn't cause that much dirty water. I admit that it's strange though - some times the water can be very dirty brown.