Claiming off home insurance for plumber's mistake

Hello Everyone,
I had a plumber fit a new heating system last year and now one of the joints he fitted has failed and caused a lot of damage. Although he has admitted using the incorrect type of fittings (against manufacturer’s instructions) he is denying responsibility – because he’s always done it that way. I have proof he used the wrong fittings and of him admitting it.
He wants me to claim off my house insurance, and they can contact his insurance company if hey want.
If I claim off my own house insurance, it will count against me and I will lose my no claims discount. Which means I will still be worse off.
Do I have any options other than small claims court?

If you try to make a claim, they may not even cover it considering how the damage occurred - depends on the exact policy details.

You shouldn't be doing the heating engineer any favours. If it's his fault, then he should pay. Whether he claims of his own insurance is his business and not yours. If he gets difficult and you have legal cover on your home insurance (often a separate item), you may want to explore whether they'll take up the case which may involve taking him to court. Otherwise just start with tying to claim the repair costs straight off him, and escalate from there, if necessary through the small claims court.

as above send your claim for damages to him and let him sort it with his insurance company.

Called my insurance yesterday, and they put me through to some legal cover I’ve got. Will see where that gets me!!
Thanks

Does the plumber have any accredited qualifications ?