Replacing tub...should I replace the drain line?

We are having new pipes installed in our home along with relocating the pipes from the slab to our attic.

At the same time we are having bathtub walls repaired due to water damage and the tub replaced.

For that bathtub should we replace the drain pipes? Is it ever necessary to replace the drain pipes for a tub? What about the other drain pipes?

It's up to you if you feel it's worth it. Does it look like the existing drains can use replacing? If things are all taken apart, you might as well anyway.

If you're having the tub replaced I always replace the waste and overflow and p-trap. the rest of the drain is usually okay, unless they are really OLD. That's a judgment call.

david is correct, replace waste an over flow along with p trap.

inspect the trap arm and determine its condition as needed

if old cast iron or galvanized..REPLACE dont even think about it,

Should I replace all the drain lines in our home or only the tub since it is convenient to do so?

What would be a good cost to do just the tub and separately all of them?

can not answer that question, to many variables. labor in your area. code in your area, prices for parts.

all of that is different state to state. do not even know if your in the US or Australia.

best for you to do, call a MINMIUM of 3 plumbers and get prices. then you will have a god idea,,whats what
look online for the cost of tubs..their are different types
you need to have an idea what kind you want, pick color after you pick type

Agree with zeppelin it's probably not much pipe and your guaranteeing yourself some time by not trusting all the hair and prior **** drained

If your opening slab and busting up concrete u might as well replace it all up to your sewer or septic with PVC OR FOAM CORE (preferably sch 40 PVC) it's not to pricey and peace of mind is priceless