Install the Well-Water Sediment Filter After the Pressure Tank Connection

For a conventional household well system, install the sediment filter on the main cold-water line after the pressure-tank connection and pressure switch, before the softener and the household plumbing you want to protect. Do not put an ordinary cartridge filter between the well pump and its pressure-tank/control assembly.

Pentair specifies installation following the pressure tank for its PC600-P/PC1000-P system, which includes a sediment prefilter. Rusco likewise places its spin-down filter on the pressure side of the pump, after the pressure tank. (Pentair installation manual, Rusco placement guidance)

The usual plumbing order

For a standard pressure-switch-controlled system, use this planning layout:

Well pump → pressure-tank tee, pressure switch and relief valve → household-side shutoff → sediment filter → softener or other specified treatment → household plumbing

The pressure tank normally connects through a branch at the tank tee; water does not necessarily flow through the tank as though it were a filter housing. “After the tank” means downstream of that connection, with the pump, tank and pressure switch still connected without a clog-prone filter between them.

Place the filter before the first branch supplying fixtures you want filtered—including the cold-water feed to the water heater. If an outside faucet or irrigation line is intentionally left unfiltered, its branch can be upstream of the filter, but downstream of the tank/control assembly in this conventional layout.

Sediment filtration generally precedes a softener so particles are intercepted before entering it. Rusco specifies this order for its spin-down filters. The order of additional treatment depends on the water analysis and equipment instructions, not simply on the available wall space. (Rusco placement guidance)

Why not put the filter before the pressure tank?

A filter creates resistance to flow. As a cartridge collects sediment, that resistance increases.

If the filter is between the pump and a tank-mounted pressure switch, pressure on the pump side can be higher than the pressure the switch senses. The pump may continue running while the tank-side pressure struggles to reach the switch’s shutoff setting. If the cartridge becomes blocked, the tank-side relief valve cannot relieve that upstream pressure. Boshart warns that this arrangement can damage the pump and filter. A larger cartridge does not eliminate the control-layout problem. (Boshart installation guidance)

With the filter downstream of the tank and switch, loading still reduces pressure available to the house, but it does not put that restriction between the pump and its pressure-sensing point. For the underlying cycle, see how a well pressure tank works.

This location protects downstream plumbing and equipment from particles. It does not remove sand before it passes through the well pump, nor keep sediment out of the pressure tank. Heavy sand therefore needs a different assessment—not simply moving a fine cartridge upstream.

The exception: a purpose-designed sand separator

A centrifugal sand separator is not interchangeable with a cartridge housing or a screened spin-down filter.

For example, LAKOS’s residential installation guide specifies separator placement between the pump and pressure tank. Its SandMaster instructions, revision 3/07, also specify the pressure switch between the separator and tank and a model-specific operating-flow range: pipe connection size alone does not determine the correct separator. (LAKOS residential installation guide, SandMaster instructions)

That is a model-specific exception, not permission to install any sediment device before the tank. Have a well contractor verify the current instructions for the exact separator, pump flow, check-valve arrangement, pressure controls and relief protection. Likewise, do not assume a constant-pressure system or a storage-tank-and-booster system uses the conventional layout above.

For screened filters, see spin-down filter sizing and placement.

Choose a location you can service

Allow for these details before changing the plumbing:

• Support and clearance: mount the housing as specified and leave room to remove the bowl and cartridge. Match the marked inlet and outlet to flow direction.
• Environmental protection: choose a location protected from freezing, impact, excessive heat and chemicals. Rusco specifically identifies these placement hazards in its guidance linked above.
• Isolation and drainage: arrange filter-service valves downstream of the tank/control assembly. Provide a suitable flushing outlet for a spin-down filter and a way to safely relieve trapped housing pressure.
• Flow capacity: select the housing and element for simultaneous household demand and acceptable pressure loss—not port size or micron rating alone. See sediment cartridge selection.

Pressure gauges immediately before and after the filter are useful for comparing pressure loss while water is flowing. Record the clean-filter difference at a repeatable flow, then follow the manufacturer’s maintenance instructions and any specified pressure-loss service limit.

Before opening a housing, isolate it and relieve its pressure according to its manual. Turning off pump power alone does not release water stored under pressure in the tank. Pentair’s service instructions require shutting off the filter supply and opening a cold-water faucet to relieve pressure. If you cannot identify the tank connection, controls and safe isolation points, have a qualified plumber or well contractor plan the installation. (Pentair installation and maintenance manual)

Finally, catching visible particles does not establish that well water is safe to drink. The same Pentair manual warns against using its system on microbiologically unsafe or unknown-quality water without adequate disinfection; sediment filtration is only one part of a water-treatment plan.