Is your intex plunger valve leaking? Then it’s probably just an O-ring. You could check a rebuild kit on amazon (SEE HERE) or just buy an O-ring that fits.
How to Fix Intex Plunger Valve Leaking
You should re-seat the outlet to the return jet by pushing it down and working fine the gasket.
The leaks with 16x 48 intex ultra are quite common. We also recommend using a fitting to connect directly to the pool.
ALSO SEE: Red Algae in Pool Filter
READ MORE: How to Fix Above Ground Pool Walls Buckling
While draining the pool to get the water line below the return level, you can take a large piece of saran wrap (any plastic wrap would work) and covered the return jet on the inside of the pool then remove the plunger valve and re-seat the o-ring while maintaining the water level in the pool.