How to renovate old ship tanks

One of the frequently asked questions when inspecting vessels, particularly older ones, is “Can I repair old tanks because I don’t want plastic or stainless steel instead?” Well of course you can, but you just have to get the job done right because the last thing you need is some heavy lifting that drips fuel or water all over the place, filling up the bilges. The top priority, of course, is safety concerns and you can be sure that if a fire or damage occurs through leaking tanks, your insurance will almost certainly be deemed null and void. In many cases the tank will be beyond redemption, but the tank can be used to allow a new tank to be molded from the old one, depending of course on your own GRP skills and the free time you have to do so. . in.

There are several stages in tank repair and certain criteria to consider before starting the job in question. Fuel tanks have a different function than water tanks, but repairs to both must be proper, safe, and robust. Materials must also be considered and a decision must be made whether the repair can be considered financially feasible, although in most cases the price of a new tank is quite appalling.


One of the questions to be answered at the beginning of the article is “Will it be an internal repair or an external repair?” Naturally, the work can make a difference if the inspection panels can be lifted immediately to allow access for repair. The other critical question is. ‘Where is it leaking and how bad is the damage?’ This can be extremely tricky and often very misleading. A small puncture leak at the edge of a tank can run several feet along pipes, go down slopes, and drip grumpily somewhere quite different, giving you bad direction! The problem can be compounded by rain or leaky pipes from above, giving the leak an added dimension. Worse, and most unfair, a tank can leak from multiple places at once, but it can go downhill in a very different place! Be careful too, the flange leak or the faucet dripping undetected along the pipe, below the bottom of the tank, gives the misleading impression that the problem is actually the tank itself. Proper leak identification is critical before tackling the big problem of removing the tank only to find it wasn’t worth it. It sounds hideously obvious, doesn’t it, but would you be surprised? Don’t be fooled by small puncture leaks too. On steel and aluminum tanks, a puncture is sometimes only indicative of a much bigger problem inside.

Many tank leaks are caused by corrosion which is the inevitable result of water remaining intact at the bottom for years. Steel tanks suffer a lot from this and often a pin leak is the first sign that the paper-thin bottom is about to fall off, in addition to the contents. Aluminum tanks have their own problems, too. Many alloy tanks are used by people and are often not marine grade aluminum alloy. This means that if left in seawater, their chances of surviving ultimate corrosion and failure are virtually nil. The wrong grade alloy literally melts into sea water! Aluminum tanks that are placed on rubber mats or padded with rubber inserts under steel retention straps can cause a lot of damage. Certain brands of rubber contain chloride and this also eats away aluminum alloys at an alarming rate. Leaving wet rags on top of alloy tanks is also bad news, as the corrosion resulting from the poultice that produces a hideous white sticky substance is also highly corrosive. Ditto for nuts and bolts and whatever tools are left on top of tanks, dissimilar metal corrosion is alive and well in these cases, all causing their own particular chaos!

Now that I’ve managed to scare them all to death, what do we have? The leak has been identified, evaluated, and the tank will likely have to come out in most cases. It’s a bit of a hassle, but overall it’s a good thing because you can check all the hidden areas not visible behind and clean them at least while the tank is out. A guy I knew did the same and found a heavy oiled bag behind the tank. Opening it found a .45 automatic pistol and a couple of boxes of bullets … what I want to know is how the hell did the previous owner forget about that? We’ll never know, I guess, maybe he never did? It was probably his wife’s! Once the tank is out, a lot will become clear. The next stage is about to evolve and we can really face the beast.


Assuming the tank has been initially emptied of contents, we can now decide, can we repair internally or not? Remove the inspection panels and decide if it is possible to work inside. Being able to see what you are doing is vital. If you have enough room to see and work, that’s great. However, a strict rule is maintained for all tanks, large or small, fuel or water, glass or metal, copper or steel, all must be impeccably clean, no grease, no rust, no dust, no silt, no dust, no particles, nothing at all. Did I clear up? Cleanliness is next to godliness in these cases, a good repair begins flawless. Once clean, it must be thoroughly degreased. For steel, copper, brass, and alloy, it helps if it’s a shiny metal too! If the bottom appears to be leaking, two coats of CSM (cut strand mat), about 1.5 ounces, will generally be enough to make sure the glass rises about ¾ inches above the bottom throughout the interior.

If further investigation of the bottom leak shows weaker metal and a larger hole (or several) appears, then it will be best to ensure that the repair is addressed from the outside. This can be achieved by backing the wet fiberglass mat with a stiff piece of cellophane covered card stock which, in turn, is firmly attached to the bottom of the tank with lots of tape. This ensures that the glass does not bend or fall or even fall under its own weight during curing. Be generous on the size of the patch, the bigger the better. Curing can be facilitated by heating with a hair dryer or even adding a little more to the resin / catalyst mixture. NO however if epoxy resin is being used … only strict measurements please! Leave a minimum of 12-15 hours, preferably overnight. Note: Gasoline tanks must be steam cleaned before any repairs are made.

Remember, in the case of fuel tanks, it is essential that the repair is completely degreased. The resin will almost certainly not stick and the process will have to be done one more time. Degreasing can be done with trichlorethylene, carbon tetrachloride, detergent solution, or a proprietary degreaser. Don’t shorten this step … you can’t say you weren’t warned!

Sealed tanks, of course, need to be repaired from the outside and it may be worth considering laying glass completely over the entire tank, especially if you use a couple of layers of fine cloth and resin filled to rinse it off. You can give your tank a new life, especially if you paint it a bright new color afterward. However, be careful that corroded parts cannot come off in the future, which could block pipes, filters and cause the engine to stop at a very uncomfortable time. One more suggestion in this scenario to ensure that there are no loose particles is to pour 2-3 liters of resin / catalyst mixture into the fill tube through a funnel to seal the bottom completely and preserve the flakes forever or loose powder after glass. the outside. It’s so cheap to make and worth the extra effort!


A leaky seam may seem like an impossible job, but with patience it is a breeze. Thoroughly clean around the seams and degrease. Just mend around the entire seam overlap on both ends of the tank.


When water tanks are repaired with general purpose resins (polyester), the styrene residue that is present (approximately 50 parts per million) imparts a “taste” to the water. It is not harmful as such, but it is quite undesirable and the flavor will linger for some time. In boats or caravans, the water is not used as quickly and it can take time to wash it off. However, certain resins recommended for drinking water supply can be used. Consult your resin supplier for advice. However, always cure water tanks for at least seven days and rinse them repeatedly with hot water, which removes much of the styrene taste. You can also steam clean the tank at your local garage for a reasonable fee … well worth it.


On a boat it is essential to always have something on hand to repair a sudden leak or a broken pipe. There are several varieties of two-component epoxy putty and epoxy pipe tapes available. Make sure the temporary repair doesn’t end up permanent though, some of these putties really work well, even soaked in fuel or water.

With today’s increasing costs, new tanks are really expensive, several thousand for large yachts, and it is always satisfying to be able to do a safe and efficient repair for a fraction of the cost of replacing them. It takes a little extra effort, but think of the hundreds of hours of work it would take to pay hundreds of extra dollars for new ones!

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