Six to twelve months for most cartridges, but that range is wide because it depends on your sediment load and how much water your household uses. The reliable method is watching pressure rather than counting months.

Why the Range Is So Broad

A cartridge filters until it is full. How fast that happens depends on what is in your water.

A home on treated municipal water with low sediment may genuinely get twelve months from a sediment cartridge. A home on a well with silt or a property downstream of recent water main work can load the same cartridge in two months.

Household size matters proportionally — a family of six pushes roughly twice the volume through the filter as a couple, and cartridge life scales accordingly.

This is why “every six months” is a starting point rather than an answer.

Use Pressure as the Signal

The most reliable indicator is a pressure drop across the filter housing.

Many whole house water filter installations include gauges before and after the filter. As the cartridge loads, the difference between those readings grows. When the drop reaches the manufacturer’s threshold, it is time — regardless of the calendar.

If your system has no gauges, they are worth adding. They convert a guess into a measurement.

Without gauges, the practical symptom is reduced water pressure throughout the house, particularly noticeable when two fixtures run at once.

Different Stages, Different Intervals

Multi-stage systems do not replace everything at once.

The sediment cartridge generally loads fastest, because it is doing the mechanical work of catching particulates and protecting the stages behind it.

The carbon cartridge is rated by volume of water treated rather than by visible loading. Carbon does not look exhausted — it simply stops removing chlorine and taste. This one has to be changed on schedule because there is no visual cue.

Specialty media for iron, sulfur, or pH correction follow their own intervals, typically longer.

What Happens If You Wait Too Long

A neglected filter is worse than no filter, which surprises people.

As a cartridge saturates, the pressure differential across it rises, and trapped material can be pushed through and released downstream. Accumulated organic matter can support bacterial growth. And restricted flow puts strain on your plumbing and appliances.

An exhausted carbon cartridge also stops protecting equipment downstream — chlorine passes through to your water softener resin, shortening its life, and to any reverse osmosis membrane, which chlorine destroys outright.

Extending Cartridge Life

If you are changing filters far more often than expected, the fix is usually upstream rather than a better cartridge.

Adding a coarser sediment pre-filter ahead of the fine one catches the bulk material and lets the finer cartridge last much longer. On well water, a spin-down sediment separator ahead of everything can dramatically reduce cartridge consumption.

Sizing matters too. An undersized filter housing loads faster and creates more pressure drop. Sizing to peak household demand rather than average use is what prevents that.

Track It

The simplest system: write the date on the cartridge in permanent marker when you install it, and log the pressure readings if you have gauges. After two or three cycles you will know your household’s actual interval, and you can stop guessing.

Buy cartridges in advance so a change is never delayed waiting on a delivery.

When to Test Instead of Replace

If filters are loading faster than they used to, something changed. A water quality test tells you whether your source has shifted, whether a well component is failing, or whether sediment is entering from your own plumbing — aging galvanized pipe sheds rust that looks exactly like source sediment.

Putting It on a Schedule

Filter changes are the maintenance most often forgotten, precisely because the system keeps producing water while quietly getting worse.

Our Care Club maintenance plan covers scheduled cartridge replacement so it does not depend on remembering.

We serve Fredericksburg, Kerrville, Boerne, Comfort, and the surrounding Hill Country. Contact 72 Degrees or call (830) 240-1835.