The short answer most people are given is every 12 to 18 months, and for a typical household that is about right. It is also what most carpet manufacturers require in order to keep a warranty valid, which is worth checking before you decide to stretch it — a warranty claim declined for lack of professional cleaning records is an expensive way to save a hundred dollars.
But the real answer depends on the house, and in Butte County there are a couple of local reasons it tends to be shorter than the national figure.
What actually shortens the interval
- Pets. Not the accidents, which are their own problem, but the dander and the oil that comes off a coat and binds soil to the fiber.
- Children, and anyone who does not take their shoes off. Most of what is in a carpet came in from outside on the bottom of something.
- Fire season. Ash reaches carpets across this county whether or not the fire is anywhere near town. It comes in through open windows and through the HVAC return, and it settles into the base of the pile where a household vacuum will not reach it.
- Harvest and field dust. Almond harvest around Durham and field work around Gridley and Biggs put fine dust everywhere for weeks.
The reason it matters more than it looks
A carpet does not usually wear out from being walked on. It wears out from being walked on with grit in it. Fine dust and ash are abrasive, and every footstep grinds them against the fiber. That damage does not come out later — a carpet that has been left dirty for four years does not clean up to look like one that has been cleaned every eighteen months, because the fiber itself has been cut.
So the interval is not really about how dirty the carpet looks. It is about how long you want the carpet to last.
How to judge your own
Kneel down in the middle of a traffic lane and in a corner the furniture has always covered, and compare them with your hand as much as your eye. If the traffic lane feels rougher or looks matted rather than just darker, the pile is already being abraded and the interval you are on is too long.
If you are not sure, ask. Our technician does a walk-through pre-inspection before any job, and part of that is telling you honestly what shape the carpet is in — including when the answer is that it does not need doing yet.