My new pump leaked into neighbour below

Hi, I had a new power shower pump fitted by reputable company.
The pump leaked once 3 weeks ago ish and the chap came back and tightened up a connection.

It has now leaked worse and possibly damaged my neighbours wooden floors.
He is directly below me.
How to proceed? I have heard the neighbour claims on block insurance, and sometimes this has a high excess which really my neighbour shouldn't pay.

Obviously I shouldn't pay either having had a pump supplied and fitted in the past few months, but I'm not going to fall out with a good neighbour over this, and if I have to I'll stump up.

Can he claim from my insurance? What about the tradesman liability?