Since all the questions you ask are highly dependent on which part of the country you live in, the best advice would come from a local pool remodeling expert. They should be able to give you a ballpark estimate so you can budget that into account for purchasing the house.

You can make a pool smaller by building a new wall or walls with in the pool, tied to the existing structure. Keep in mind depending on the layout, some returns, suction lines, skimmers, new tile or lighting may have to be factored in. This is not an uncommon request in the remodel market, normally people request addition of wetdecks or raising the floor of a deep pool. Process is essentially the same. Cost is relative to size and who is doing the work, I would estimate a starting point of $7,000, this would not include back filling and finishing ( landscaping/hardscape) the abandoned section of the pool.

Enlarging or reducing is not as complicated as it sounds but do make sure you ask your contractor to give you ref. on a reduce job and GO SEE IT. You'd be surprised how many people alter size so should not be hard to find a contractor. Harder to find b/c time of year but not b/c of work scope.

Thanks for the responses. We are in San Antonio, TX. We have figured the cost of removing the pool into our purchase, but we want to explore the option of retaining a smaller pool, maybe just a lap pool. The present pool is a simple rectangle with lots of dated and poorly kept hardscape around it. The previous owners/sellers basically hardscaped almost the entire backyard. We will be removing most of the hardscape anyway in favor of landscaping.

After 40 years I would demo and build your dream pool with all new plumbing and equipment. To build a pool inside another shell will cost the same as adding a new pool and you will be covering over some issues that will surface later. The only expense this route has would be the demo which sounds like you were doing lots of that already. I know of some great pool builders in San Antonio

We met yesterday with a PB named Jim Wanamaker of Liquid Assets. If you have a confidential opinion of him to share, it would certainly be appreciated. Thanks jim@nineflamingo.com

I would suggest getting at least 3 bids on your project to compare and gain information to make a wise choice. I do not personally know Jim but am very familiar with River Oaks Pools which was part of PACE which I was part of and they built a great product.

In the same dilemma now

Would like to reduce the length of the pool> Can i use concrete blocks for the wall, then cement over it? They would be tied into the wall of the current pool. The drain is a problem being it's in the deep end. What do you recommend?

Im shorting the pool by 3’ & adding short baja step question is what material is used to fill pool before cement?

Consult a structural engineer who has pool experience.

Anytime we have added, steps, benches or shelves, we drill and pin rebar into the existing structure and shoot all concrete.