Bathtub pinhole leak repair

furletcityNovember 21, 2009

Our 2nd floor bathtub has been unusable due to a small drip(onto our new cherry kit cabs!) when used. After much investigation we finally discovered a pinhole leak in the bottom of the tub(older fiberglass?) that is unnoticeable from the topside. We have pretty good access to the leak.Is there a patch meant for this that someone can reccommend? Thanks in advance!

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Fortunately for you, this is a fiberglass tub, and unlike acrylic, fiberglass is relatively easy to repair.

Fiberglass tubs, shower enclosures, and sinks are fundamentally made in the same manner as fiberglass boats and automotive body components.

I once had opportunity to tour a factory where they made both boats and bathtubs. To my complete surprise, the first step of the process is to apply the trim decals to the interior of a mold, then the "Gelcoat" finish is sprayed into the mold. After the gelcoat finish has hardened fiberglass cloth, matt or a chopped fiberglass material called roving is mixed with a hardening resin material and it is applied to the inside of the mold until the body of the product is built up to the finished thickness. The mold is then set aside for approximately 24 hours to allow the fiberglass to cure, then they apply a high pressure air hose to a nozzle on the bottom of the mold, air is injected into the mold to separate the finished product from the mold, and once it separates the finished product is lifted out.

The good news is that fiberglass is very easy to repair or maintain unfortunately the manufacturers of fiberglass tubs and showers often fail to inform the consumer of how its done.

To maintain the original luster you can wax the surface with the same fiberglass wax that is used for boats and automobiles, however it should be noted here that when waxing a tub or shower you should only wax the walls, not the bottom of the tub or shower, which would cause a slip hazard.

As fiberglass ages it will often oxidize and take on a dull lifeless chalky appearance. When that happens the original luster can easily be restored by using fiberglass rubbing compound and a buffer, followed by waxing in the same manner as shinning a car or boat.

In the case of a minor hole such as you describe you can go to any auto parts store, marina or in most cases in the sporting goods section of your local walmart, or Kmart and find a fiberglass "GelCoat" repair kit.

In the kit you will find a chemical cleaner, a small supply of emery cloth abrasive, a container of white "Gelcoat" material and a number of small containers containing colored pigments which can be mixed with the Gelcoat to produce an exact color match to your tub. (Usually the color pigments are blister packed in the retail container so you can be sure to get the proper color pigments to match your finish).

You begin by buffing the repair area with the emery cloth. You then place a small amount of the white gelcoat in the supplied plastic mixing tray and add pigments, mixing well, until you get an exact color match. The material is then applied to the hole, smoothed out and allowed to harden for the specified time. After it hardens you buff it out with the fine emery cloth supplied in the kit and you will have a watertight, almost invisible repair.

If the hole is larger than about 1/8" diameter you may want to reinforce the repair area. If so, you can get a "Fiberglass repair kit that has a small quantity of fiberglass cloth, fiberglass resin and hardener. You mix the resin and hardener per mfg instructions, then dip fiberglass cloth strips in the mix and apply it to the underside of the tub under the hole to build up a repair patch.

In most cases fiberglass repair is easy, however, if you feel uncertain about your ability to do it, I would suggest you go to an auto body shop or marina and find a mechanic that is familiar with fiberglass repair and see if he or she would be willing to take on a small side job.

    Bookmark   November 21, 2009 at 11:52AM
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Thank you so much for the detailed info, lazypup!!

    Bookmark   November 22, 2009 at 11:03AM
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Thanks for the info. I just bought a surfboard (fiberglass) with some cracks in the rails, blue in color. I just might try to repair it myself.

    Bookmark   November 23, 2009 at 7:52AM
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The first time I actually saw a tub refinished we were doing a complete rehab in a motel that had 200 guest rooms with fiberglass tub/shower enclosures. The tubs were originally a proprietary design used by the motel chain and they insisted that we replace the tub/showers with an exact match which would have required a custom production run from the manufacturer at a cost of over $900 per unit.

We were debating the pro's and con's of having the tubs custom made, plus the labor required to remove and replace the existing tub when one of our apprentices came forward and said that he had formerly worked in a marina repairing fiberglass boats. He said he could refinish the existing tubs in place in about 4hrs with a material cost of about $15 per unit. At first we were all skeptical until he said he would come in on Saturday and do one tub on his time and materials with the understanding that if we were happy with the results he would get a contract to do the rest. What did we have to loose? If he was right it would save thousands of dollars and hundreds of man hours. On the other hand, if he was wrong we could just rip the tub out on Monday, which was the original game plan, so we were out nothing.

When we came in the following Monday morning, not only did we find what looked like a brand new tub/shower enclosure, he had also cut in through the adjacent wall and replaced the tub mixing valve leaving only a minor sheet rock repair to complete the job.

Needless to say, we gave the young man his contract, and when we completed the motel job, the motel neckties were so impressed they hired that man full time to work for corporate and travel from one motel to the next refinishing tubs.

    Bookmark   November 23, 2009 at 9:16AM
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That's a good story. Thanks, LP.

Also, I know of more than a few fiberglass showers that could use a face lift. Glad to hear about these methods.

    Bookmark   November 24, 2009 at 7:42AM
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