WC LIMESCALE REMOVAL heavy: How to avoid damage to plastic connector seal of WC pan to drain? Will acid drain cleaners like "ONE SHOT" DAMAGE THIS PLASTIC?

Hi Chemicals like Oneshot or dambuster won't damage plastic, otherwise they couldn't put it in a plastic bottle. They only dissolve organic matter. Hope this helps. Fred.

Best product if you can still get hold of it is powdered citric acid. 100% natural and reacts with limescale disolving it and causes no damage to plastic etc. You used to be able to buy this in the chemist years ago?