Short definition
A drain-and-waste valve combines a shutoff with a small bleed or drain port on the downstream side. Closing the valve isolates the upstream line; opening the bleed releases the trapped downstream water to atmosphere. It’s the standard fitting for winterizing exterior or unconditioned-space lines, especially on WA second-home properties.
What it is
Mechanically, it’s a ball-valve or globe-valve body with a small set screw or knob on one side that opens a 1/8-inch or 1/4-inch port to atmosphere on the downstream side. With the main valve closed, opening the bleed lets air in (or water out) so the trapped downstream water can drain out by gravity instead of staying in the line where it can freeze.
The terminology is unsettled — “drain-and-waste” and “stop-and-waste” describe the same fitting. Some sources use one term exclusively, others use the other; treat them as synonyms.
Why it matters to a homeowner
The whole point is winterization. WA has substantial second-home and cabin stock — Hood Canal, San Juans, Whidbey, Methow, Leavenworth, Olympic Peninsula — where freeze-burst is a real risk if the supply piping is left charged over winter. A drain-and-waste valve at the start of an exterior or unconditioned line means winterizing becomes a single operation: close the main, open the bleed, the line drains itself.
Three common applications:
- Outdoor sillcock supply line. A drain-and-waste valve indoors at the line’s start lets the exterior section drain back when shut off in fall.
- Vacation-cabin supply. Drain-and-waste valves at strategic low points let the system winterize fast.
- Irrigation entry. A drain-and-waste valve on the meter side of the backflow assembly allows full system winterization.
Common failure modes
- Bleed port plugged with mineral or scale buildup — won’t drain when needed. Diagnose during fall winterization, not during a January cold snap.
- Bleed port leaks past the set screw — slow drip during normal service.
- Same shutoff-side failures as any ball- or globe-valve body.
Common variants and what it isn’t
- Drain-and-waste vs. stop-and-waste. Same concept; different sources use different names.
- Drain-and-waste vs. drain cock. Drain cock is just a drain port — no integrated shutoff. Drain-and-waste includes both.
Washington note
For any WA property used seasonally, drain-and-waste valves are part of the winterization-ready piping design. Annual fall winterization protocol on a typical cabin: turn off the main, open every faucet to relieve pressure, drain the water heater via its boiler drain, open every drain-and-waste valve at every low point, and blow compressed air through hose bibs and exterior runs to clear horizontal standing water. Spring re-pressurization reverses the process.