I don’t know how to find this guy’s leak, but there was an episode of Dirty Jobs that shows how to make a NYC rooftop cistern out of yellow cedar. It’s pretty much a tutorial on how to make one, so I’m sure it contains useful information on how to fix one, too. Here’s an episode recap http://www.tv.com/dirty-jobs/dirty-jobs-of-the-big-apple/episode/1167649/recap.html
Don’t do anything quite yet, particularly fiberglassing. All you need is a bucket of cedar sawdust. Fill the tub, throw in the sawdust and let it do its thing. The sawdust will seek the leak, fill the gaps and keeo your tub full. Keep extra sawdust around just in case. I’d hate to see you add any chemicals or glass in the tub. Good luck.
As a wooden boat owner your problem sounds familiar. For advice and local supply of products, check to see if you have a local wooden boat mechanic. If you are do it yourself type, there are many methods (and many products) for sealing wood planks available at most internet boat supply stores (they also carry fiberglass products). I personally use an adhesive/sealant on large seams with excellent results (no leaks in the boat), you can get these products in tubes for your calk gun and force it into cracks after draining your tub and letting it dry a few days. There are lots of types to choose from, primarialy differing in the ability to take it apart in the future (easy - difficult - perminant). I have used a medium grade sealant (can be removed with difficulty) on a large gap several years ago and have had no further problems. Fiberglas works best to repair small damaged areas as an alternative to replacing the whole plank.
What T & R failed to mention is that automotive cooling system sealant is not really something that you would want in a hot tub or anything else that your skin and private parts will be in contact with for an extended period of time. Even if it worked to seal the leaks in that tub, this is not something that you would want someone (particularly women) to be coming into contact with.
If the cedar tub dried out heat and moisture should reseal the wood as it rehydrates and expands the wood. However you could also refinish the interior using a clear resin based product that would protect the wood
EdS has got the right idea! In fact wooden boat builders would do this in reverse, and go under the leaky boat and let the sawdust go up. So go get some cedar sawdust.
Then you can think about whether or not you need to use some epoxy resin on the bottom of the tub. You can get clear resin, and mix some of the sawdust into it, or you can get resin, and laminate cedar veneer into the bottom of the tub.
Some really hotshot boats (custom built high end yachts) are built with this technique – laminating wood veneer with resin – I think it’s called “cold molding” or something like that.
I think a stop leak product for an auto radiator would make a big smelly mess, and might wreck the whole thing. I would strongly suggest you discard that idea. Good Luck!
I built a 600 gallon indoor koi pond using a ring of milk crates banded with a burly car tow strap, draped with an outdoor pond liner. It works great!!! I suggest going to lowe’s (or equiv), getting a pond liner, then follow click-clack advice by using pond liner (+ silicon), then putting faux layer of cedar down to keep vibe of unit.
Actually, sawdust idea is trick. Try that first. If all else fails, pond liner will work.
I fixed a redwood hottub several years ago with clear silicone seal. The leak may be in the groove where the staves contact the bottom. Water gets in there (from anywhere) and can travel in the groove. I drilled from outside into the groove and used a tube of clear silicone seal injected with a caulking gun. You may need to do this every 12 inches or so. The tub does not need to be empty. Good luck.
Stop leak for radiators is water glass, sodium silicate. It is safe to use for a hot tub. Just buy a gallon of water glass from a farm supply store. It is commonly used to seal drinking tanks for cattle. SOME stop leak has powdered aluminium or brass added so you don’t want to use that kind in a hot tub. Sodium silicate hardens to a quartz like substance in the presence of CO2 so you can speed up the process by spraying a can of CO2 on the outside of the tub wherever you see water leaking. I’ve used water glass mixed in sand to make metal casting molds. A quick shot of CO2 hardens the stuff instantly.
Eggs are also coated with water glass to make them last longer since it fills the pores in the shell and keeps air out.
The stuff is incredibly benign.
It won’t seal a huge gap in the staves; cracks are what it seals best.
EdS has it right. I use it in my hot tub. Staves shift and warp.
Worms nibble holes though the wood. The sawdust will find the leak and plug it.
If you can take the time to dry the thing out VERY well, consider “penetrating epoxy” – an epoxy product that will basically petrify the wood (employing the wood fibers rather than glass fibers as the reinforcement for the plastic/resin).
Buuuut . . . once it’s dry, the boards will have shrunk, and maybe better would be to drive in cedar wedges (shingle ends) along the central seam in the bottom, and maybe one or more seams around the sides, and then refilling it. The swelling of the re-wetted wood should seal any leakage.
Expands when wet to tightly seal cracks.
Traditional leak sealant in waterworks.