HI – I would only eliminate a main drain if you have a significant issue with it being broken or leaking that is not easy to get to – ie if the broken pipe is buried underneath the patio and a full renovation is not possible at this point.

If you are replacing a vinyl liner and you have a single drain, you should have the drain modified to add a second drain for the current anti-entrapment regulations – and for safety of swimmers using the pool. This is something an experienced team can do when the liner is being replaced and isn’t a huge expense, though it will cost a bit – mostly in labor to add it.

There are typically two locations on a pool that water is “drained” from the pool and circulates into the pump and equipment, those are the main drain(s) and skimmer(s). You need enough water flow for proper filtration – so again, eliminating one only makes sense if it is your only option.

I have also not ever heard that main drains are the first to fail. We’ve been servicing vinyl liner pools for decades, and some of the original pools built by our company at 20+ years old have properly functioning main drains with no issues…