Boiler water treatment

[Jeff Layman]

Anyone know what the colour of the water would be in a CH system treated with an inhibitor?

Twice in the last few days we've found 1 - 200 ml of dark brown oily water on our gas hob, and the extractor filter badly stained. I thought first of all that it was rain driven in through a leaky chimney, but that had been repointed, reflashed, and reflaunched less than 3 years ago. And we had the nasty fluid on the hob today when there's been no rain. The fluid seemed to be coming through the hob extractor fan, but on removing it the vent through an old chimney was dry. What was wet was the brick edge going up into the loft (this is a bungalow). Despite a careful search I could find no evidence of a leak in the loft, but the most likely spot was covered by the hot water tank.

It's taking a lot of time to clean up the mess. Any ideas other than inhibitor-treated HW being the fluid on the hob?

Photos at:

[Animal]

Some is clear, some is brown, most I won't buy so don't know.

[Brian Gaff]

If its coming down the brick though, maybe in the short term a partial baffle to stop it going to the extractor and redirect it somewhere harmless might be worth the effort. A sheet of metal with a tilt and aimed at a void? Brian

[Jeff Layman]

It was the old chimney, but exactly how the gunge trickled down is unclear, as there's still no sign in the loft. There was once a fireplace in the kitchen, but it was removed at least 25 years ago. The old chimney is still in place (there is another one adjoining which the logburner in the lounge uses). The kitchen chimney acts as the vent for the hob extractor, but it was completely dry and clean and is 40 or 50cm from where the gunge was dripping. The logburner chimney is even further away.

A roofer went up this morning and found a cracked tile by the flashing. He reckoned the recent very cold weather had frozen water in the crack and opened it up. A few other tiles and a ridge tile were replaced as they were possibly suspect (the roof is 57 years old).

It struck me that this might not have happened if the loft wasn't so well insulated. Heat would have risen to the ridge and possibly kept the tiles warm enough to prevent them freezing.

I'm just hoping I don't have to clear up a mess for the third time!

[Davidm]

in the hot water tank developed a leak allowing hot water from the tank to get into the CH water supply. Fortunately the pressure in the HW tank was slightly higher than the CH system, or the contamination could have been much more serious. Took ages to diagnose the slight overflow from the CH header tank. New tank and fitting, £700!

[Harry Bloomfield Esq]

The inhibitor is clear/colourless, as should be the contents of your central heating radiators and system. Brown, suggests rust, which comes from your radiators rusting, which the inhibitor is intended to prevent

- unless it was omitted at some time in the past?

[Jeff Layman]

No. We had a new boiler about 3 years ago, and the whole CH system was power-flushed, and an inhibitor then added. Also, as part of the new boiler installation a magnetic filter was put in the circuit. I thought the outside was glass, allowing me to see if the colour of the contents was brown. But on inspection it wasn't possible to see inside.

However, as reported in my follow-up, it was the chimney and not the CH system.

[The Natural Philosopher]

Rust requires oxygen, and that means you must have been constantly filling up the primary circuit with fresh oxygenated water due to a leak.

I though the general sludge was sulphides, along with hydrogen gas being produced

No idea how sulphides get there though.