Haven't heard of any
fuel tank problems. Those are
stainless steel (at least on my boat).
There have been problems with some of the
aluminum fresh
water tanks due to chlorine in the water reacting with the metal. Not really welds failing, just
corrosion, which tends to produce pinhole
leaks if it's allowed to go unchecked.
Most complaints were about aluminum chloride crystals clogging up the
water pump strainer or faucet aerators. Using a carbon canister filter on "city" water (the chlorinated kind), solves the problem easily. I have the aluminum water and holding tanks on my
boat and after I figured out the chlorine thing, never had any issues.
I understand the newer IPs are being fitted with
fiberglass water and holding tanks.