The relay takes the load for the pump ensuring that the existing gas box switch only takes the load of the relay contacts.This enables thicker cable to be run to the pump and minimises voltage drop.
I would only expect it to affect the warranty if it caused parts to fail and as the external pump and pump saver are non standard anyway they would be covered by their own warranty.
The seal between the existing socket and the van body is not affected as the contacts can be fitted to the original Whale shell(as I found out after buying the whole lot)
It then requires the existing fill pipe from the inlet to be disconnected (and plugged)and a new length of water pipe from the inlet to the tank.
Bailey have just drilled a hole in the top of the tank for the existing pipe and you would need to do it in the same way for the new fill pipe.
------------- John
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