Custom potable water bladder

[David97]

I am curious about your experience with custom potable water bladder installed in fiberglass tanks (mine haven't been coated with an epoxy for drinkable water and it would require a lot of work to properly coat them). Have you used the bladders for extended offshore sailing? Have you lined the tanks to protect the bladder? After how many years of use have they failed? Any vendor you would recommend?

[GordMay]

Have your fiberglass tanks been, previously, utilised for fuel?

[David97]

No. Water only. I was thinking using a Seagull filter but I am not sure if they can filter chemicals that could be leaching from the polyester resin.

[GordMay]

Ensure that your proposed bladder material is resistant* to Styrene, and MEK.
* won’t be degraded by, nor allow to pass through.

It's the styrene, in the polyester resin, that can leach out. The curative agent (methyethylketone or MEK) is also very toxic, and acts like a true catalyst, in that is facilitates the reaction, but does not actually get incorporated into the chemical chain, so any amount used, is thereby, free to work its way out from the resin, and into your tank.

[Nanamuk]

We use stock Vetus Hypalon bladders in our 2 aluminium water tanks. The inefficient filling of the available volume means we lose a couple of gallons of capacity, more so when we tried using a liner. Without the liner the tanks, which we secured on all 4 corners, have lasted more than 15 years including a 7 year circumnavigation. The only leak we have had has been where a fill distorted the hole in the tank as the stiff attached hose didn't move as freely as the tank when it was only part full and sloshing around in a rough sea. Repair was to glue on a patch with a new hole resulting in 2 layers captured in the fill unit. I don't know what the risks or the solutions may be to leaching of bad things from the fiberglass but if there is no smell now in either the empty tank or when you boil water from the tank I personally wouldn't worry about using a bladder.

[Reeve21]

I used a Vetus bladder for 10 years or so to add extra capacity, so not inside a tank, in a locker against the hull.

Did not have any issues with leaking or smell/taste.

It worked for me. Boat was used for coastal cruising only.