I have a designer acrylic tub with hot tub jets in them as well. It is about 5-6 years old. I bought the house 2 years ago.

It leaks from where the tub meets the tile right behind the faucet. I can see that the caulking (which is about 1.5 years old) is split. I cut a hole in the ceiling in the basement and I can see the water is dripping down from approximately that area.

I think that the tub was not properly supported when installed and hence when it is in heavy use (I have 4 kids), it flexes up and down, deteriorates the caulking and starts to leak. I fixed the leak 1.5 years ago for 3-6 months by re-caulking.

Is there any way to shore up this tub or stiffen it or strengthen it so that it doesn't flex without tearing apart the whole bathroom?

Is there a super heavy duty caulking that will flex with the tub and not split open that someone can recommend?

I have a designer acrylic tub with hot tub jets in them as well. It is about 5-6 years old. I bought the house 2 years ago.

It leaks from where the tub meets the tile right behind the faucet. I can see that the caulking (which is about 1.5 years old) is split. I cut a hole in the ceiling in the basement and i can see the water is dripping down from approximately that area.

I think that the tub was not properly supported when installed and hence when it is in heavy use (i have 4 kids), it flexes up and down, deteriorates the caulking and starts to leak. I fixed the leak 1.5 years ago for 3-6 months by re-caulking.

Is there any way to shore up this tub or stiffen it or strengthen it so that it doesn't flex without tearing apart the whole bathroom?

Is there a super heavy duty caulking that will flex with the tub and not split open that someone can recommend?

If you're saying the leak is behind the chrome face plate on the faucet get a tube of Dap White Tub and Tile Caulk, clean out the old caulk loosen the face plate and pull it out a bit. Squeeze a ring of Dap around under vthe plate and tighten it back down. Now run a ring of Dap around the outside, smooth it out with your finger and let it set up and cure.
As for the tub flexing, anything under there to support the bottom would be helpful. We puddle and build up mounds of cement or mortar to support the base. Good luck, Tom

I think you have SELF-RIMMING TUB installed as TILE OVER TUB. If that's true than it is wrong. The Tile Over Tub has a lip that goes up the wall and drywall / hardi-backer board over it. It seals against leaks . Self Rimming Tub doesn't have it. Therefore, yes, it will leak.

Some manufacturers actually offer "L" moulding that can be silicone on self rimming tub making it suitable for Tile Over situation. But that would have to be installed before walls are tiled...

You don't have too many options dealing with this problem. Take the caulk out, buy SANDED CAULK to match the grout and caulk it. Caulk is flexible and will absorb some movement.

As far as the tub support goes: you have to pack some light weight concrete under the bottom of the tub.

Can you take picture of the tub and the edge and post it ?