Pentair Grid Assembly for FNS Plus 36 | 59023500

Pentair FNS Plus 36 Complete D.E. Grid Assembly (Element Cluster) | 59023500

The Pentair 59023500 is a factory replacement complete element grid assembly for 36 sq. ft. vertical-grid D.E. pool filters. This pre-assembled grid cluster replaces the internal grids and manifold/collector assembly to restore proper filtration when your existing grids are torn, cracked, warped, or heavily coated with scale and oils that won’t clean out.

Compatibility

• Fits: Pentair FNS® Plus 36 / FNSP36 vertical grid D.E. filters (where parts diagram specifies 59023500)
• Also used on: select Titan RPM 36 sq. ft. vertical grid D.E. filters (where parts diagram specifies 59023500)
• Tip: Confirm your filter model and square footage (36 sq. ft.) before ordering—grid assemblies are not interchangeable across sizes.

Key Features

• Complete 36 sq. ft. grid set: replaces the entire internal grid pack for consistent filtration performance.
• Pre-assembled cluster: designed to drop in as a complete assembly (reduces install time vs. replacing individual grids).
• Restores water clarity: fresh grid fabric helps capture fine debris when properly charged with D.E.
• Fixes D.E. blowback symptoms: helps correct D.E. returning to the pool caused by torn grid fabric or broken frames (after confirming the air relief and internal seals are in good condition).

What’s Included

• Complete internal grid assembly for 36 sq. ft. FNS Plus-style filters
• Grid count: typically 7 full grids and 1 partial grid (pre-installed in the cluster)
• Manifold/collector components and tie rods as supplied with the complete assembly

Specifications

• Brand: Pentair
• Part Number: 59023500
• Filter Type: D.E. (vertical grid)
• Filtration Area: 36 sq. ft.
• Grid Height: approx. 18" (overall installed height varies slightly by assembly/manifold measurement)
• Quantity: 1 complete grid assembly (cluster)

Common Reasons to Replace

• D.E. powder returning to the pool (torn grid fabric, broken grid frame, or damaged manifold)
• Persistent cloudy water even after proper backwash/cleaning and correct D.E. recharge
• Cracked/brittle grids from age, chemical damage, or freeze conditions
• Major filter rebuild where you want all-new internal filtration surfaces

Installation Notes

• Shut off the pump, relieve pressure at the air relief, and open the filter per manufacturer procedure.
• Remove the old grid assembly, then clean debris from the tank bottom and inspect the standpipe and sealing surfaces.
• Reinstall the new assembly, ensuring it seats fully and aligns correctly before closing the tank.
• After restart, recharge the filter with the correct amount of D.E. for a 36 sq. ft. filter (follow your filter manual for exact dosing).

Related Products

• Search Aqua Pool Supply for 59023500
• Pentair FNS Plus 36 (FNSP36) replacement parts
• D.E. filter powder
• FNS Plus tank O-rings
• D.E. grid cleaner / degreaser
• Silicone lubricant for O-rings (filter-safe)
• Filter air relief assemblies

Maintenance Tips

• Backwash/clean on schedule and recharge with the correct D.E. amount—running undercharged can reduce clarity and increase grid loading.
• Deep-clean grids periodically (degrease, then descale if needed) to prevent oils and minerals from permanently restricting flow.
• Always relieve pressure before opening the filter, and inspect the tank O-ring each time you service the unit.
• Maintain balanced water chemistry to reduce scale buildup that shortens grid life and hurts filtration performance.