c_lark

On our property we had some volunteers build a stone hot tub at the top of a hill. The tub is natural stone (gathered from the site) with mortar in between. We didn't really know what we were doing, but what we've built is beautiful and we'd like to try and fix what we have rather than tear it apart. Apparently, when we built it, we should have used waterproof mix-ins for our mortar (because mortar, like all concretes, is porous). Do we have any options for making it a bit more watertight? 100% watertight isn't necessary as the tub is only filled for a few weeks out of the year for events, but it would be nice to not have to refill it as often as we do now. Currently it does hold water but needs a top-off every 2-hr or so. We do not want to use a pool liner since that would ruin the natural beauty that we have. Anything that completely covers the inside surface is also a no-go. Could we use an epoxy pool paint or some kind of sealant just over the mortar to seal it up a bit? What about a pool plaster? Do you think that work if it's only applied in certain areas? Any help is greatly appreciated. Thanks, Clark