I agree with Roger that I think the anode needs to be located close and in the same electrolyte rather than just bonded. If not I would be able to just have one anode attached to the bottom of the swim platform and make checking and replacement easier.

    I don’t know of any suppliers in the marine environment but we did used to get the race car exhausts coated internally with an epoxy paint to help with gas flow, perhaps coating the water trap internally with epoxy resin may offer some protection from corrosion. It might be worth looking into the costs of an epoxy coating at some point.