Black gunge

Yuck; looks evil! Presumably some sort of slime mould or algal growth. If it were mine, I'd scrape away as much as possible, generously spray the inside of the cistern with bleach or other mould killer, and then suspend a Loo Blue or similar in the cistern.

Bleach. Oh, and leave the EU.

I used anti freeze in the empty cistern and in the bowl and it worked. I don't know why.

In message , Muddymike writes

Quatermass 2?

We have one toilet plumbed to soft water (convenient for the plumber:-( That develops dark streaks inside the pan. I wonder what it would develop into if cleaning lady didn't get there first.

Do you use any of those nasty drop in supposed cleaner small nice products in the cistern? I found these seem to go very messy after a time and then nasty stuff starts to grow and propogate. the only option is to drain it all down and clean it all with bleach or something like that. Yuck. Brian

Do you recall the hippo supposedly to save water? These weighted sponges seem to promote growth of slime mould I ditched mine some years back. Brian

No Hippo or additives have been used by us. STWNFI has now doused the inside of the cistern with bleach.

That caused an entertaining foam eruption in the bowl first time she flushed it:-)

Mike