How do i plug a leak on the bottom of my 5,000 gallon well water tank? Help!?

I can patch the side leaks on me metal tank easy enough with marine epoxy.
but there's no way i can crawl in the tank without destroying the bottom with my weight.
i would like to find something i can pour in there that would sink and find the hole and cover it up. wouldn't take much with the water pressing against it.
maybe some sort of saw dust? it would eventually sink and find the leak? but it can't rot over time or have bad chemicals in it...
 or something made of much smaller particles?

really needs to be a remedy tested by time, maybe something from our grandfather's day.

or, i could make a remote controlled robot with manipulators and a camera!


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Kiteman7 years ago
If you can see the hole, why not make a seal from rubber, and lower it over the hole with a pole? Maybe put a "bead" of epoxy around the rubber to make a better seal?
abraxas1 (author) 6 years ago
so, what i ended up doing is sliding in a wedge under the small gap under the tank between the support wood. i made a two piece ramp system.
i slid one piece underneath the hole, and it had a lift at the end, so when i slid the other piece over that one, it pressed up into the tank only where the hole is.
still leaks slowly, but nothing important.
ordering a big plastic tank now. hoping to get someone to take away this giant piece of rusted steel for free.

thanks all,
abraxas1 (author) 7 years ago
Lots of great ideas!
I could imagine lowering some patch with epoxy down there, but it would have to be big and probably won't adhere too well.
I was hoping for a sort of "nanoparticle" answer in that you would throw a few handfuls of something in there (saw dust?) and it would sink and, eventually, surround the hole and gently block it.

i think a new tank is in the future!
Thanks all who contributed!
what great responses.
erik_mccray7 years ago
so if you can fill it but it just has a small leak fill it say a little less then your arm length get in there on a flotie & fit it with some underwater epoxy.
Thinking about it: Onrust has a good plan, but it might be better to work some fibreglass over the whole INSIDE of the tank - but the fumes from the resin will be really nasty.
Fiberglass WITH milled fibers..... rust is not smooth OR easy to patch.
Granted ! I was thinking tissue might be reasonably effective, but really, this tank is dead isn't it ?
onrust7 years ago
Is it out of line to say get a new plastic tank before you wast anymore $$$$?
NachoMahma7 years ago
. If the tank is so bad that it won't hold your weight then you can expect to replace it soon, especially if you keep the tank very full.
.  Not sure what the average density of a person is, but, since we are mostly water, it's bound to be close to the same. Ie, six feet of water will exert approximately the same PSI on the tank bottom as a six foot tall person standing there. If you keep three feet of water in the tank, that half a human standing there all the time.
.  You may be able to buy some time with epoxies, bladders, &c, but I'd start saving for a new tank.
I dunno, some folks can be denser than lead.
lemonie7 years ago

is the whole thing rusty, or just wrong in one spot?

onrust7 years ago I have seen this used many times but potable water????hell who knows! not to mention your "tank" is bigger
+1 on the epoxy lining, also POR15 do a tank lining polyurethane coating.