Stain on wood floor- ufh leak or chemical reaction?

1 Apr 2022
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United Kingdom
I spotted this dark stain on my wood floor around 3 weeks ago, last time the underfloor heating was on was in December. Yesterday I switched it on again and it seems to be getting bigger. The stain is dark, no cupping or crowning, no sign of water or moisture. Any ideas whether it's a chemical reaction or an actual leakage please.The flat is 8 years old and the wood plank is in front of the door where the water cylinder and manifold are. Thank you.


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Looking at it, it doesn't suggest a leak from below, simply because it seems to be in the centre of the wood rather than at the joints of the planks. Water will find the easiest path and I would suggest the joints would typically be where a leak would show first. Of course that wouldn't be definitive until a closer look confirms.
Thanks a lot for this Madrab. Doing my research an actual ufh leak would be pretty obvious but it's really odd it's changing colour/ shape after 8 years. It looks like a oily wood stain job gone wrong....

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