Short definition
A compression faucet is the oldest still-common faucet design — a threaded brass stem with a rubber washer at the bottom. Turning the handle drives the stem down, compressing the washer onto a brass seat to close flow. Standard in pre-1980 WA homes, and the reason “fixing a faucet” used to mean “replacing the washer.”
What it is
Each handle on a compression faucet controls one stem assembly. From bottom to top: rubber washer (held by a brass screw), threaded brass stem, packing washer or string around the stem at the top, packing nut, and a larger bonnet nut retaining the whole stem in the body. Below the washer, screwed into the body, sits a separate brass valve seat.
Closing the handle drives the stem down. The rubber washer presses onto the brass seat. If both surfaces are clean and undamaged, water stops. If the washer is worn or the seat is pitted, water leaks past — that’s the drip.
Service intervals in normal use: rubber washer 5 to 15 years; brass seat 20 to 40 years before pitting; packing 10 to 20 years.
Why it matters to a homeowner
If you have a two-handle bath or laundry faucet in a pre-1980 Capitol Hill bungalow, a Tacoma craftsman, or a Spokane mid-century, the dripping faucet is almost certainly compression. Repair is honest DIY: turn off water, pop the index cap on the handle, remove the set screw, lift the handle, unscrew the bonnet, unscrew the stem, replace the rubber washer at the bottom.
The trap: if the brass seat is pitted (often the case after decades of WA water), no new washer will seal. Cranking the handle harder makes it worse — you’re driving fresh rubber into a sharp pit. The cure is a seat wrench to remove the seat and a $3 replacement, or a seat-grinding tool to resurface it.
When a plumber says “I’ll re-seat and re-washer the faucet,” that’s this procedure. Annual washer replacement is not normal — if you’re doing it every year, the seat is the real problem.
Common failure modes
- Worn rubber washer. Drip from the spout. Most common faucet drip on pre-1980 fixtures. $3 fix.
- Pitted brass seat. Washer can’t seal even when new. Replace or resurface the seat.
- Failed packing. Leak under the handle when running. Re-pack with graphite string or replace the packing washer.
- Stripped stem threads. Replace the stem assembly.
- Galvanically stuck stem. Penetrating oil, gentle heat, basin wrench.
Common variants
- Compression vs. cartridge. Compression has separate hot/cold handles each with a stem-and-washer; cartridge has a single sealed insert.
- Compression vs. ceramic-disc. Compression uses a rubber washer; disc uses ceramic-on-ceramic.
- Compression vs. fuller faucet. Fuller is a quick-acting low-pressure variant common in old wash basins; closes a rubber ball against a seat.