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In most pressure-pump systems, install the spin-down filter after the pressure tank, not between the pump and the tank.
A common layout is:
Water source → pump → pressure tank and pressure switch → spin-down filter → finer filters or fixtures
This setup lets the pump and pressure tank work together without a clogged filter getting between them. It also makes the spin-down filter easier to service without changing how the pump senses system pressure.
There are some systems where a spin-down filter can go before the pressure tank, but that placement needs more care.
Why After the Pressure Tank Is Usually Better
A pressure tank stores a small amount of pressurized water. It reduces how often the pump has to start and stop.
The pressure switch tells the pump when to run. For example, it may turn the pump on when pressure drops to a set point and turn it off when pressure rises again.
The pressure tank and pressure switch should normally have a clear, unrestricted connection to the pump.
If you place a filter between the pump and the tank, sediment can slowly clog the filter screen. That creates resistance to flow.
The pump may then produce higher pressure on its side of the clogged filter while the pressure tank and switch see lower pressure on the other side. Depending on the system layout, this can interfere with normal pump control.
Putting the spin-down filter downstream of the pressure tank avoids that problem.
A Typical Layout
For a rainwater system with a pump and pressure tank, a simple arrangement may look like this:
Rainwater tank → pump → pressure tank tee → spin-down filter → finer filtration → irrigation or household non-potable lines
The pressure tank tee may also hold the:
- pressure switch
- pressure gauge
- pressure relief valve
- drain or service connection
The exact parts depend on the pump and pressure system.
The spin-down filter then catches sand, grit, rust flakes, insects, or other larger particles before they reach smaller filters, valves, irrigation equipment, or fixtures.
Why You Might Want the Filter Before the Pressure Tank
There is one clear reason to consider putting a spin-down filter before the pressure tank: keeping sediment out of the tank and pressure components.
This may be useful where the incoming water contains a lot of sand or coarse debris.
Spin-down filters are often less restrictive than cartridge filters. Water enters the filter body, and heavier particles collect near the bottom where they can be flushed out.
But "low restriction" does not mean "no restriction." A dirty screen can still reduce flow.
For that reason, putting one between the pump and pressure tank should only be done when the pump, filter, pressure switch, relief protection, and plumbing arrangement are designed for it.
For a basic DIY system, downstream placement is usually simpler and safer.
Do Not Put a Fine Cartridge Filter Before the Pressure Tank
A fine sediment cartridge is much more likely to create a noticeable pressure drop as it loads with debris.
Avoid arrangements such as:
Pump → fine cartridge filter → pressure tank
A clogged cartridge can severely restrict the pump's connection to the pressure tank and pressure controls.
If you need several treatment stages, a more typical arrangement is:
Pump → pressure tank → spin-down filter → sediment cartridge → other treatment
The exact treatment order should match the intended water use.
Where Should the Pressure Switch Go?
The pressure switch should normally sense pressure on the same side of the system as the pressure tank, with as little restriction between the pump, switch, and tank as the system design allows.
That is why many pressure systems use a tank tee. The tank, switch, gauge, and pump connection are grouped together.
You generally do not want a filter that can clog separating the pump from the pressure switch.
Some pumps use electronic pressure controls instead of a traditional pressure switch. Follow the pump manufacturer's plumbing layout in those systems.
What About the Pressure Drop Across a Spin-Down Filter?
Every filter creates some resistance.
The pressure loss may be very small when the screen is clean and become much larger as sediment builds up.
How much pressure is lost depends on factors such as:
- filter size
- screen size
- flow rate
- amount of sediment
- plumbing diameter
- how often the filter is flushed
Flow rate means how much water moves through the system during a given time, usually expressed in gallons per minute or liters per minute.
A filter that works well on a small garden line may be too restrictive for a larger pump feeding several fixtures at once.
Choose a filter that can handle the system's expected flow and pressure. Do not reduce a large pump discharge line unnecessarily just to fit a smaller filter.
What Micron Size Should a Spin-Down Filter Use?
The micron rating describes the approximate size of particles a filter screen is intended to catch. One micron is one-thousandth of a millimeter.
Spin-down filters are generally used for relatively coarse sediment rather than very fine filtration.
Reviewing practical considerations for a spin-down filter worth it helps assess treatment needs for the way the household will use the water.
The right screen size depends on what you are trying to protect.
For example, a coarse screen may work well as the first filtration stage before an irrigation system. A finer downstream cartridge may then catch smaller sediment if needed.
Do not choose the finest screen simply because it sounds better. A very fine screen may clog quickly and reduce flow.
For rainwater systems, good debris control should also begin before the pump. Gutter screens, inlet screening, settling, and suitable prefiltration can reduce the amount of debris that reaches the pressure system.
What If the Water Comes From a Rainwater Tank?
With stored rainwater, try to keep large debris out of the pump in the first place.
A system may include:
Roof → gutters → leaf screening → first-flush or inlet treatment → storage tank → pump → pressure tank → spin-down filter
A first flush system diverts some of the first roof runoff so that dirt and debris from the roof are less likely to enter storage.
A spin-down filter should not be expected to fix poor collection or dirty storage conditions. It is one sediment-control stage.
If the water is used only for irrigation, the main goal may be protecting pumps, valves, drip emitters, and sprinklers.
If rainwater will enter household plumbing, treatment requirements become much more important.
Does a Spin-Down Filter Make Rainwater Safe to Drink?
No.
A spin-down filter removes some physical particles. It does not provide complete treatment for bacteria, viruses, dissolved chemicals, or other contaminants that may be present in roof runoff.
Potable water means water suitable for drinking. Non-potable water is water not intended for drinking.
Using collected rainwater as potable water requires a whole-system approach. That can include suitable collection surfaces, debris control, storage management, treatment stages, disinfection where appropriate, maintenance, and current laboratory testing.
Local plumbing and health requirements may also apply.
Do not treat a spin-down filter as proof that rainwater is safe to drink.
Make the Filter Easy to Flush
Placement should also allow routine maintenance.
Leave enough room around the filter to:
- see collected sediment
- operate the flush valve
- attach a drain hose if needed
- remove the screen for cleaning
- inspect fittings for leaks
Route flushed water somewhere that can safely accept it. Avoid creating slippery areas, erosion, or water damage around pumps and electrical equipment.
If the system is outdoors in a freezing climate, the filter body and flush valve also need appropriate freeze protection. Trapped water can expand when frozen and damage housings or fittings.
When to Get Professional Help
Get help from a qualified pump or plumbing professional if the proposed layout places a filter between the pump and its pressure controls, especially on a larger pressure system.
Professional help is also sensible when the system includes:
- high pump pressures
- large cistern pumps
- household plumbing
- multiple pressure zones
- electrical pump controls
- pressure boosters
- complex treatment equipment
Improper pressure-control plumbing can damage equipment or create unsafe pressure.
Bottom Line
For most simple systems, put the spin-down filter after the pressure tank.
A practical order is:
Pump → pressure tank and pressure switch → spin-down filter → finer filtration or water-use lines
This keeps a potentially clogged filter from interfering with the connection between the pump, pressure tank, and pressure switch.
Putting a spin-down filter before the pressure tank can help keep sediment out of the tank, but only when the pump controls and pressure protection are arranged correctly for that design.
Frequently Asked Questions
Can a spin-down filter go before a pressure tank?
It can in some systems, but it is not the best default layout. A clogged filter between the pump and pressure tank can interfere with pressure sensing and flow. Use that arrangement only when the pump and pressure-control setup is designed for it.
Should the sediment filter go before or after the pressure switch?
In a typical pressure-tank system, the pressure switch should be on the pump and tank side of the sediment filter. This keeps filter restriction from separating the pressure switch from the pump.
Will sediment damage a pressure tank?
Sediment can collect in plumbing and equipment, although the effect depends on the tank design and the type and amount of sediment. Keeping debris out of stored water and maintaining good prefiltration can reduce the problem.
Should a spin-down filter go before a cartridge filter?
Usually, yes. A spin-down filter can catch larger particles first, helping reduce the sediment load reaching a finer cartridge filter.
Can I install a spin-down filter directly after my rainwater pump?
Only if doing so does not put the filter between the pump and the pressure tank or pressure-sensing equipment in a way the pump manufacturer does not allow. In many pressure systems, the tank connection comes first.
How often should I flush a spin-down filter?
Flush it often enough that collected sediment does not noticeably restrict flow. The needed schedule depends on water quality and use. Inspect it frequently when the system is new, then adjust the maintenance interval based on how quickly debris builds up.
Does a spin-down filter reduce water pressure?
Yes, although the pressure loss may be small when the filter is properly sized and clean. Pressure loss increases when the screen becomes dirty or when the filter is too small for the required flow.
