Every time it is used , the bathtub is flooded.Ihave used many chemicals to no avail.I tried using a small hose to the drain but it could not go inside the drain.How is the drain constructed? Thank you for your help.

Your drains need snaked... Time to hire a plumber.

Hey Smoothy. Did you forget that the reason we're here is so the OP doesn't have to hire a plumber?

Hi Tubby and welcome to The Plumbing Page at AskMeHelpDesk.com.
I'm no fan of putting harsh chemicals in your drainage. Besides, they only work in TV ads.
You're snaking from the wrong place. Let me show you how it should go.
You have a blockage downstream from the tub. The solution would b e to snake the drain line from the tub overflow.
Unscrew and remove the overflow plate,(The one with the drain lever) and pull out the tub stopper. You now have a clear shot at the trap. The way you were going in through the drain it ran you square into a tee that you can't get around. Now feed the cable( 1/4" best or 3/8" with a small tip. You can rent a Ridgid K50 sink cable.) About 2' down you will run into the bend of the trap. Crank and push at the same time to work around it. Your blockage will be found in the lateral pipe going to the stack. You shouldn't have to put out more then 10 or 12 feet. I have found tub and shower clogs to be mostly hair and the worm should auger into it and pull it back. After you snake pour a few pans of boiling water down the drain. This will loosen the grease and flush the mess out into the main. Hope this helps and thank you for rating my reply. TOM