My project involves removing an existing 5 foot by 28 inch wide bath tub and installing in its place a 6 foot by 36 inch whirlpool. I have check out all the details and I have the room needed to fit the tub and do the installation properly and also handle the electrical. However I am a novice when it comes to plumbing. It turns out the existing waste drain on my bath tub is 13 inches from the long wall and 8 inches from the drain wall. The new drain on the whirlpool will have to be 17 7/8 inches from the long wall and 12 inches from the drain wall. My question is can I purchase a new waste-and-overflow unite which can be adjusted to mate to the existing drain trap in the floor. I have not removed the tub yet to take a look but I need to know if I need to move the floor drain trap and in that case I will need to call a plumber. If I can purchase an adjustable waste-and overflow unite that is adjustable to over come this 4 inch by 5 7/8 inch change in drain location on the whirlpool waste drain I can complete the job myself without the added expense of calling a plumber in. Is this type of adjustable waste-and-overflow unite available; or can I order a PVC version that I can add pipe to adjust the length to fit the drain?

If the old drains is PVC, this will be a good first plumbing project. PVC is easy to work with. If you have access to the old drain, just cut it off beyond the trap. Leave a couple of inches of straight pipe if you intend to reuse the trap. If the new whirlpool tub doesn't come with a drain, you may be able to unscrew the old one from the tub and reuse it. Identify the pipe size. The most reliable way is what is printed or molded into it. If it says 1 1/2, that means 1 1/2'' pipe. It will be slightly larger than 1 1/2'' inside. It should also say DWV. You will need a short length of pipe, a coupling or 2, and maybe some elbows. Be very careful to use DWV elbows. They have a longer radius and are made to be harder to clog up. Better to use 45 degree ones if you can. Pick up a can of primer, and cement. Assemble everything without any cement. Once you are sure everything fits, clean up the pipe good, primer, and cement following the directions on the can. The cement sets almost at once. Still, there is hardly anything you can't fix with a hack saw and another coupling.