The Correct Order for Well Water Treatment Systems

The order you install well water treatment equipment matters, because each tank protects the one after it. Every filter goes after the pressure tank. The sediment filter comes first, the iron filter goes ahead of the water softener, and the UV light goes after the filters and the softener. If your pH is low, an acid neutralizer goes in too, and I set its place from your test.

This page goes through each piece in order, why it sits where it does, what goes wrong when the order is off, and the common combinations a water test calls for.

The Full Treatment Sequence

Water flows from your well to the pressure tank, then through each piece of treatment equipment in this order before it reaches your faucets. Each piece has one job, and each one protects the equipment after it. Tap a photo for the product page.

	Order after the pressure tank	Equipment	Why it goes there
	Before any treatment	Pressure tank	It holds the water pressure for the house. Nothing goes between it and the well pump.
	1st	Sediment filter	Catches sand and grit before they reach the valves and tanks after it.
	2nd	Iron filter	Takes out iron, manganese and the rotten-egg smell before they reach the softener.
	Your test decides where it goes	Acid neutralizer, if your pH is low	I set its place from your test. It goes ahead of the softener.
	3rd	Water softener	Removes hardness, including the hardness the neutralizer adds.
	4th, if you want one	Carbon filter	Improves taste and smell. It goes after the softener and before the UV light.
	5th	UV light	Kills bacteria. It needs clear water, with hardness under 7 grains, to work.

An under-sink reverse osmosis system for drinking water, if you want one, goes at the kitchen tap after all of these. If you are just starting out, my well water filtration guide goes through what each tank does, how to size it and what it costs.

Why Nothing Goes Before the Pressure Tank

Every filter and treatment tank goes after the pressure tank, never between the well pump and the tank. A caller in June was planning an acid neutralizer in a crawl space and asked where it goes. I told him: "After the water tank. You can't, you can't obstruct the flow to the water tank. It creates, that creates pressure for your house."

Boshart, a maker of well tank fittings, gives the reason. The pressure switch sits at the tank. A filter ahead of it clogs as it catches dirt, the switch cannot read the pressure the pump is building behind the clog, and the pump keeps running until it burns itself out. Before new treatment goes in, have a licensed plumber or your well driller check that the tank is in good shape. My pressure tank guide covers the tank itself.

The Sediment Filter Goes First

The sediment filter goes first after the pressure tank and catches sand and grit before they reach the valves and tanks after it. As I put it in the video, it is your first line of defense. I recommend the 20 inch Big Blue with a 5 micron cartridge. The quick check: lift the lid off the toilet tank you use most, and if there is dirt settled in the bottom, you need one.

A spin-down screen is different. If you have one, it goes after the treatment tanks, where it catches any media the tanks let past. My sediment filter guide covers the types and where each one goes.

Where the Acid Neutralizer Goes

If your pH is low, an acid neutralizer goes in too, and I set its place from your test.

The neutralizer's calcite adds about 4 to 6 grains per gallon of hardness, so the water softener goes after it. If you have low pH and iron over about 0.5 ppm, a backwashing neutralizer keeps the calcite from fouling with iron. The iron filter works best near pH 8, so if your pH is lower, send me the report before you order. My guide to running an acid neutralizer with a softener covers that pair.

In the video above, the iron filter goes ahead of the neutralizer. That was one customer's water, with high iron, low pH and a sulfur smell; yours may call for a different order, and I set it from your test.

The Iron Filter Goes Before the Softener

The iron filter always goes ahead of the water softener. High levels of iron shorten the life of the softener's resin and can foul it, and a softener is not an iron filter, so do not count on one to take the iron out. When a buyer with an iron filter and a softener asks which tank goes where, I tell them: "the iron filter goes first in line after the pressure tank."

Both tanks clean themselves on a timer, so the second thing I tell those buyers is to set the two clocks apart: "set the iron filter for the correct time and set the softener for 2 hours difference, so they never backwash together." My iron filter guide and water softener guide cover sizing each one.

The Carbon Filter Goes After the Softener

A carbon filter is optional on a well. It is there for taste and smell, and it goes after the softener and before the UV light. Carbon also reduces some PFAS, but which treatment fits depends on what your PFAS test finds. My carbon filter guide covers the types.

The UV Light Goes After the Filters

The UV light goes after the sediment filter and any iron filter or softener, because it only works in clear water. VIQUA, the maker of the UV lights we sell, says the UV should be the final piece of treatment equipment, with a 5 micron sediment filter ahead of it. It also calls for iron under 0.3 ppm and hardness under 7 grains per gallon going in; harder water should be softened first. My UV light guide covers sizing and the yearly lamp.

Reverse Osmosis Goes Under the Sink

A reverse osmosis system is for drinking water only. It sits under the kitchen sink and treats the water at that one tap, after the whole-house tanks are in. It is not part of the whole-house line. My guide to reverse osmosis for well water covers when it makes sense.

What Happens When the Order Is Wrong

A wrong order can make equipment stop working properly or wear out early.

Common System Combinations

Most homes do not need every tank. Your water test decides which ones you need. Each line below starts after the pressure tank.

You also do not have to buy everything at once. If acidic water is the main problem, a sediment filter and a neutralizer may be all you need to start. Retest after it goes in, because the neutralizer can raise the hardness enough that you add a softener later. My guide to reading your well water test results goes number by number.

Have a test and not sure of the order?

Send Aidan your test results

Send your water test results to Aidan. He'll tell you exactly which systems you need and in what order, based on your specific water chemistry. There is no charge for this consultation.

Text Aidan443-277-2204 Call800-460-5810Aidan

8 AM to 5 PM Eastern, seven days a week. A real person, not a call center.

Plan the Layout With Your Plumber

We recommend installation by a licensed plumber, and I help your plumber by phone at 800-460-5810. Every tank ships empty; the media comes in separate bags and is loaded at install. Drain tubing is not included, and the backwashing tanks need a drain nearby. Plan the whole layout before anyone cuts pipe, so each tank has room for its bypass valve and for service, and nothing has to be moved later because the order was wrong.

Frequently Asked Questions