Hi I have a built it fibreglass water tank, which seeps into nearby compartments. I can't find the sorce of leak, is there a waterproofing product I can paint inside the tank that's good for drinking water?
What have others done?

This may not answer your question but does water come out the lids? On my boat these leak.

If you fibreglassed the tanks, wouldn't it be best to scuff back and paint a thickened fibreglass resin in the tank to catch the pinholes. Titanium dioxide is a cheap and harmless filler to thicken up the resin. Or just use a gelcoat resin if you made them out of poly.

Note West System Epoxy is not recommended for water tanks.

There's a range of acrylic water proofing products available & some are for potable water check at the big green shed. Looks like a testing job if they're much more than 400mm deep, possibly easier to start again

I had same problem in previous boat in all tanks (300 litres) and installed bladders. Worked perfectly with a filter to remove any taste change.

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Madmouse said..
This may not answer your question but does water come out the lids? On my boat these leak.

Not from the lids as when there halve full they start leaking

I would suggest a visit to a real hardware store and buy a product used to paint inside water tanks.

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sunycoastguy said..
Hi I have a built it fibreglass water tank, which seeps into nearby compartments. I can't find the sorce of leak, is there a waterproofing product I can paint inside the tank that's good for drinking water?
What have others done?

Waterdye will should you the source of the leak.

I use epoxy for my tanks and they are fine but it looks like yours are poly. If you can remove the tanks I would sand them and put two layers of nice fine surfboard cloth over the tanks. Heavier fabric has more chance of pinholes.

Thanks for the reply, I found the leak!! I drained the tanks then next day saw a brown, tea coloured water leaking back into the tank. So I fibreglass that section up, will fill it up tomorrow, but confident that was the leak.