Pentair Grid Assembly for FNS Plus 36 | 59023500
Pentair
SKU: 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.
Questions about returns? View our return policy.
Hours Of Operation:
Monday - Friday: 7:00 am to 5:00 pm Phoenix Time
Saturday: 8:00 am to 2:00 pm
Sunday: Closed
- We do not ship on Saturday or Sunday.
- Orders totaling more than $300 will require signature confirmation upon delivery.
- We process and prepare orders for shipment within 1 business day. Please note that many other pool supply retailers require 3–5 days of handling time before shipping.
- Orders placed after 1:00 pm Phoenix Time may not be eligible for same-day shipment.
- Expedited shipping options are available at checkout.
Return Policy:
- Products that are received damaged will receive a refund in store credit.
- Most products are eligible for return within 30 days of receipt, except where noted below.
- To initiate a return, please complete an RMA form prior to sending your item back.
- Original shipping costs are non-refundable and will be deducted from the return credit.
- Items returned missing accessories or original packaging, or that are not in the same condition as received, may be subject to a restocking fee of up to 100% depending on the condition of the item upon return.
- Some returns will be charged an automatic 15% restocking fee.
- We are unable to issue refunds for items that have been damaged or rendered inoperable due to installer error.
- Please complete the return form to receive your RMA number and return shipping label.
- Chemical products are not eligible for return under any circumstances.
- The Pentair Colorsync 618031 is not eligible for return.
- Pool cleaners are not eligible for return.
- Opened seals and o-rings are not eligible for return.
- Capacitors are not eligible for return.
- Plastic popup tools are not eligible for return.
- Automation components and circuit boards are not eligible for return.
- If a light is returned due to a reported malfunction and is found to be fully operational upon testing, return shipping costs and a restocking fee will be deducted from the refund.
- Orders refused at the time of delivery will be subject to the original shipping costs being deducted from the refund.
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