The Pentair Pentek Big Blue housing itself lasts about 10 years under normal use. The filter cartridge inside needs replacing every 3 to 6 months, depending on your water's sediment load. If you notice reduced water pressure, the cartridge is full and needs changing sooner. Heavy-sediment wells may need monthly cartridge changes — in those cases, consider adding a spin-down pre-filter upstream to extend cartridge life.

This kit uses a 20-inch Big Blue housing that accepts standard 4.5" × 20" cartridges. The overall dimensions are 7" × 7" × 21". The 20-inch size provides roughly double the surface area of a 10-inch Big Blue housing, which means longer filter life between changes and better performance in high-sediment wells. We also carry a 10" Big Blue kit ($165) for tighter installations.

Every 3 to 6 months under normal conditions. The exact interval depends on how much sediment is in your well water. Signs it is time to change: reduced water pressure, visible discoloration when you remove the cartridge, or a pressure gauge reading showing more than a 5 PSI drop across the housing. Some well owners with very sandy water change cartridges monthly. At $10 to $20 per cartridge, it is the cheapest protection for your downstream treatment equipment.

The included 5-micron cartridge is the most common choice for well water. It catches sand, silt, rust, and fine sediment without restricting flow. If your water has very fine particulates (like clay), you may want a 1-micron cartridge — but it will clog faster. If you have heavy coarse sediment, start with a 20 or 50-micron cartridge and use the 5-micron as a second stage. The housing accepts any standard 4.5" × 20" Big Blue cartridge. See our micron ratings guide for detailed recommendations.

Standard polyspun cartridges are not washable — once loaded with sediment, they need to be replaced. However, you can buy pleated cartridges for this housing that are washable and reusable. Pleated filters have more surface area and can be rinsed clean with a garden hose. They cost more upfront ($20 to $30) but last longer between changes. For heavy-sediment wells, a pleated washable cartridge can save money over time.

After the pressure tank and before everything else. The correct order is: well pump → pressure tank → sediment filter → iron filter → acid neutralizer → water softener → UV system. The sediment filter is always first in the treatment chain because it protects every piece of equipment downstream. Sand and grit will damage valve seals, clog filter media, coat UV quartz sleeves, and shorten the life of every system it reaches.

The 20-inch Big Blue has roughly double the cartridge surface area of a 10-inch, which means it holds more sediment before needing a change and handles higher flow rates without restricting pressure. The 20-inch is better for homes with 3 or more bathrooms, heavy sediment, or multiple treatment systems downstream. The 10-inch Big Blue ($165) works fine for smaller homes with low to moderate sediment. Both use the same 4.5" diameter cartridges — just different lengths.

A clean sediment filter causes minimal pressure drop — typically 1 to 3 PSI. As the cartridge loads with sediment over time, the pressure drop increases. When you notice reduced flow at your faucets, it is time to change the cartridge. The 20-inch Big Blue housing is designed for high-flow applications (15 GPM) specifically to minimize pressure loss. Installing shutoff valves on both sides of the filter makes it easy to isolate and change the cartridge quickly.