I have repaired smallish leaks with various patches. They never hold once winter and freeze/thaw returns.
But there is hope. If you have buckets for horses, then you have horse poo. Scatter the leaky buckets in the garden and flower beds at strategic locations. Fill 2/3 full of horse poo add water until they are full and let them leak away. Presto. Slow drain watering and fertilizing....
hot melt glue gun. The tip is hot enough to melt the poly of the bucket. Plus swirl a bit of the glue into the melting bucket to weld the edges together. The key is melting the bucket material more than applying glue to the bucket.
Look in the phone book or Google "plastic welding" and you can usually find a local person to do this job for a very reasonable price. They can also weld plastic wheelbarrows,shovels, etc. so it might be worthwhile to take bunch of stuff at once.
Huh, I've never had a water bucket crack (I live in NH, yes we have ice). Don't thump on the pails, flip them over in the sun and let the ice melt out in a chunk.
That's all well and good if you are doing chores during daylight hours, and you have time to wait around for anything to melt when it's a bright and cheery -25C day.
I hold the buckets by the handle and kick them a couple of times -- co-ordinate the swing with the kick for more force (if it's not a frozen solid block of ice) and usually it bounces right out. I've never had a fortiflex bucket crack. I much prefer them to the rubber which gets "fuzzy" over time.
Why must you chastise my brilliant idea with facts and logic? **picks up toys (and wine) and goes home**
Another option for emptying frozen buckets-- this assumes you have a water trough with a heater in it. I just toss the bucket-sicle in the trough and let it bob around overnight. By morning it's an empty bucket. Setting them upside down in the sun works great too--doesn't take long for the outer layer of ice to melt. BTW the water trough method is a great way to thaw a frozen hose.
I recommend just buying a complete extra set of buckets. In the mornings, swap the frozen bucket for an empty one, and set the frozen one aside, in the sun or water trough. The one-time cost to buy buckets is worth it for the time, frustration, and cracked buckets it saves.
(also note that unless you get ALL of the ice out before refilling, your new water will freeze much more quickly. The pre-existing ice creates more surface area that the water is in contact with)
no ideas for patching but the cracked bucket can be demoted to feed bucket.
I also know the absolute best item for deicing a bucket is a bowling pin. Use it like a mallet on the outside of a bucket or trough. it will not crack a bucket unless the bucket is frozen solid. the pin absorbs the shock.