Fuel and Water Tank Repair and/or Restoration

[Lefty]

Sent: 5/8/2007

One of the most common problems encountered by members, is that the fuel tanks are in need of either repair or cleaning due to the amount of time they have sat with fuel in them. Thankfully, we are not alone in this problem. This is also a common issue for fuel and water tanks in large boats (such as cabin cruisers).
I ran across the following excerpt from an article located here:
http://ezinearticles.com/?How-To-Renovate-Old-Boat-Tanks&id=545878

Quote:

THE REPAIR ITSELF
Assuming the tank to have been initially emptied of content, we can now decide, can we repair internally or not? Remove any inspection panels and make a decision whether it is possible to work inside. Being able to see what you do is vital. If you do have enough room to see and work that?s great. However, one steadfast rule remains for all tanks, great or small, fuel or water, glass or metal, copper or steel, they must all be spotlessly clean, no grease, no rust, no dust, no slime, no powder, no particles, no nuthin. Did I make myself clear? Cleanliness is next to godliness in these cases, a good repair starts spotless. Once cleaned, it must be degreased thoroughly. In the case of steel, copper, brass and alloy it helps if it is shiny bright metal too! If the bottom appears to be leaking two layers of CSM (Chopped strand mat) about 1.5 ounce mat will usually suffice ensuring that the glass is raised about ¾ inches above the bottom all round inside.

If further investigation of the bottom leak shows weaker metal and a larger hole appears (or several) then it will be best to ensure the repair is approached from the outside. This can be achieved by backing up the wetted fibreglass mat by a stiff piece of cellophane covered card that, in turn, is stuck firmly to the bottom of the tank with plenty of sticky tape. This ensures the glass will not sag or droop or even fall off under its own weight whilst curing. Be generous in the patch size, the larger the better. Curing can be facilitated by heating with a hair dryer or even adding a little extra to the resin/catalyst mix. NOT, however if epoxy resin is being used?..strict measures only please! Allow a minimum of 12-15 hours, preferably overnight. Please note: In the case of petrol tanks, they must be steam cleaned before any repairs are undertaken

Remember, in the case of the fuel tanks, it is critical for the repair to be completely degreased. The resin will almost certainly not adhere and the process will have to be re-done once more. Degreasing can be done with trichlorethylene, carbon tetrachloride, detergent solution or a proprietary degreaser. Don?t shortcut this step?..you can?t say you weren?t warned!

Sealed tanks of course, must be repaired from the outside and it may well be worth considering, to completely glass over the whole tank, especially if you use a couple of layers of fine cloth and used filled resin to fair it off. You can give the tank a completely new lease of life, especially if you paint it a bright new colour afterwards. However, be careful that any corroded pieces cannot break away in the future, potentially blocking pipes, filters and causing the engine to stop at a very awkward time. One further suggestion in this scenario to make good and certain that no particles are loose is to pour 2 to 3 litres of resin/catalyst mix down the filler pipe via a funnel to seal the bottom completely and preserve forever any loose flakes or dust after glassing the outside. It is so cheap to do and it is worth the extra effort!

THE LEAKING SEAMS
A leaking seam may seem an impossible job but with patience it is a breeze. Clean thoroughly all around the seams and degrease. Simply repair right around the whole seam overlay on both ends of the tank.

A WORD ABOUT WATER TANKS
Where water tanks are repaired with general purpose resins (polyester) the residue of styrene that is present (about 50 parts per million) imparts a ?taste? to the water. It isn?t harmful as such but quite undesirable and the taste will hang around for some time. In boats or caravans the water does not get used so quickly and it can take time to flush away. However, certain resins that are recommended for drinking water supplies can be used. Check with your resin supplier for advice. However, always cure water tanks for at least seven days and repeatedly flush with hot water, which removes much of the styrene taste. You can also have the tank steam cleaned at your local garage for a reasonable fee?it is well worth it.      : /End Quote

While the above material was written for fuel tanks located in a boat, the same general principles apply. Especially the part of coating the insides with 2-3 litres of liquid fiberglass resin to permenantly stop rust particles from getting into the fuel system, and to prevent future leaks. I found this particularly interesting, because I have applied fiberglass to the outsides before, but never poured the resin into the tank and coated the interior. A great tip.

[Elandan2]

You will find many posts here about "welding" cracks in your polyethylene tank. Or new tanks are available from Winnebago. You can find the diagrams and part numbers here: http://www.winnebagoind.com/service/wincd/1979/79common.pdf
starting on page 51 of the document.