Should I Cap Old Pool Return Lines When Installing New Pipework and Recasting the Shell?

Since you’re:

• Installing a completely new pipe system,

• Building a new pool shell 4–5 inches inside the existing one,

• And the old eyes (return jets) are located in the outer wall,

• Essentially creating a “pool within a pool”,

Here’s the answer:

Yes, you absolutely need to cap or seal the old eyes and plumbing.

Even though the new shell will be inside the old one, the old penetrations (eyes, drains, pipes) in the outer wall can:

• Leak water into the old void space between the two shells

• Create pressure buildup, water stagnation, or mildew

• Eventually compromise the integrity of your new structure if water migrates back or seeps in

---

How to properly handle the old eyes:

1. Cut back the old pipes a few inches from the wall if accessible.

2. Cap with a PVC plug or a proper pressure-rated end cap.

3. Seal around the cap and pipe entry point with hydraulic cement or expanding pool putty (e.g., A+B epoxy or similar).

4. Fill the void space in the pipe with foam or sand for added protection (optional but helpful).

5. If possible, pressure test to confirm no leaks remain.

Once sealed, treat the old shell like a formwork or containment for the new one. Your new structure should be completely independent and watertight.