A mattress protector is the cheapest insurance in the bedroom and the item most likely to be ruined by the person who bought it.
Not through neglect. Through washing it the way you wash everything else, which destroys the thing that made it work.
If you have ever had a protector that crinkled loudly, felt like a garbage bag, or stopped keeping anything out, it was almost certainly laundered to death rather than defective.
How a protector actually works
A waterproof mattress protector is a fabric top layer bonded to a thin membrane, usually polyurethane. The fabric is what you feel. The membrane is what does the job.
That membrane is a plastic film thin enough to breathe and flexible enough that you cannot detect it. It is also the most fragile component in your bedding, and three ordinary laundry habits destroy it.
High heat. Polyurethane softens and then degrades well below the temperature a hot dryer reaches. It does not fail all at once. It stiffens, becomes brittle, and starts cracking in the places that flex most, which is why protectors fail along the fold lines and at the corners first.
Fabric softener. Softener works by depositing a waxy coating. On a protector that coating sits on top of the breathable membrane and clogs it. The protector goes from breathable to a sheet of plastic, which is why it starts sleeping hot and feeling clammy. This one is permanent.
Bleach. Chlorine attacks the bond between the fabric and the membrane. Once they start separating you get bubbling and peeling, and there is no repairing it.
Washing one properly
Cold or warm water. Never hot.
Gentle or normal cycle, ordinary detergent, and about half of what you would normally use. Protectors are not very absorbent by design, so the detergent has nowhere to go and residue builds up on the surface.
No fabric softener, no dryer sheets, no bleach. If you want it softer, that is not what a protector is for.
Wash it with sheets rather than towels. Towels shed heavily, and the lint mats into the protector’s surface fabric.
Do not wash it with anything that has a zipper or a hook. A snag that punctures the membrane ends the protector, and you will not notice until something gets through.
Drying, which is where most of them die
Low heat or no heat. If your dryer has an air-fluff or air-dry setting with no heat at all, that is the correct one.
Take it out slightly early and let it finish on a rack or over a door. The last few minutes in a dryer are the hottest, and that is where cumulative damage happens.
Air drying is genuinely the best option, and in Tempe it is fast. A protector on a rack indoors dries in a couple of hours most of the year. Keep it out of direct sun, since UV degrades polyurethane the same way heat does.
No ironing, ever, for reasons that should be obvious.
How often, and how many
Every time you wash the sheets is ideal, since the protector is the layer taking the hit. Every other time is realistic and fine.
More often if someone is sick, if a pet sleeps on the bed, or if you sweat heavily, which through a Tempe summer is most people.
Own two. This is the advice people skip and then regret at midnight. One on the bed, one clean in the closet. It means you can strip and remake immediately rather than waiting on a cycle, and it means the protector actually gets washed rather than getting put off because the bed would be unprotected in the meantime.
Encasements are a different item
A fitted protector covers the top and sides. An encasement zips fully around the entire mattress, all six surfaces.
Encasements are what you want for allergen control or if you are worried about anything getting into the mattress from underneath. They wash the same way, with one addition: do the zipper up before washing, and be careful with it, because a zipper is the most likely thing to snag.
Encasements are bulkier than they look. A king encasement is a large item and it needs room to move, which many household washers do not have once you factor in the water.
When to replace one
Protectors are consumable. Two to five years is normal, less with heavy use and hot drying.
Replace it when you see cracking or peeling on the underside, when it has gone stiff or crinkly, when water beads on top and sits there instead of the protector simply feeling dry, or when something has clearly gotten through.
Hold it up to a window. If light comes through pinholes, the membrane has failed.
Where the size becomes the problem
King protectors and full encasements are large, and they need water volume and room to tumble to rinse properly. Packed into a household drum, the detergent stays in the folds and the surface never fully rinses, which is its own path to a clammy protector.
The machines at our self-service laundry on Broadway have the capacity for a king encasement plus a full set of sheets in one load, which is the natural way to wash them together.
Our wash-dry-fold service handles bedding if you want it done without the temperature questions.
The short version
Cold or warm water, half the detergent, no softener, no bleach, no towels in the load. Low heat or no heat, and finish it on a rack. Own two so it actually gets washed. Wash it every time or every other time you do the sheets. Check it against a window once a year and replace it when the membrane starts letting light through.
WaveMAX Tempe on Broadway is at 1845 E Broadway Rd, convenient across Tempe and the neighborhoods along the Broadway corridor. If you are not sure whether a protector is still doing its job, our contact page reaches the store and we are happy to talk it through.