Leak only when hose left pressurized

Quick Answer:

If a spigot only leaks after a hose has been left pressurized overnight, the fixture is likely weeping under sustained pressure. Start by turning the spigot off and opening the hose end overnight to confirm the condition, then inspect the internal seat or any backflow/check device for small slow weeps. You can often bench-test or replace a bad seat yourself; if the backflow device is failing or the bib body is damaged, call a pro.

Why This Happens

Garden spigots and their internal seats are designed for short bursts of pressure, not constant, long-term stress. When a hose stays attached and full of water, the constant pressure can force water past a weakened rubber seat, worn O-ring, or a failing check valve. Small defects that don’t show up under brief use may weep slowly after hours of steady pressure.

This is similar to a Hose bib leaks under pressure issue and can share causes with a Leak appears only during heavy use situation — worn seals, trapped debris, or a backflow/anti-siphon device that no longer seals perfectly under sustained load.

Step-by-Step What to Do

1. Reproduce the condition safely

• Turn the spigot off and open the hose end (or remove the hose) so water can drain. Leave it like that overnight. If the spigot does not leak after the hose is drained, sustained pressure was likely the trigger.
• If you have an inside shutoff for that exterior bib, close it first so you can work dry and safe.

2. Inspect the exterior and backflow/check device

• Look at the vacuum breaker or backflow assembly (if present). After pressurization you may see slow, steady weeps from the unit or at the bib-thread joint.
• Note where water appears: from the handle/stem, at the valve seat inside, or through the backflow housing. This tells you whether the internal seat or the backflow is failing.

3. Cycle the valve and bench-test the seat or backflow

• Shut the water supply to the bib. Remove the backflow device or unscrew the faucet bonnet to access the seat and washer if you are comfortable doing that.
• With the part removed, operate it and look for visible wear, hardening, or grooves. You can bench-test a backflow device by pressing or actuating it off the fixture and checking that seals close under short pressure bursts; do not create high sustained pressure on the bench test.
• If you’re unsure, take the old part to a hardware store or compare to repair kits before buying replacements.

4. Replace the failing seat or install a pressure-relief device

• Common fixes: replace the internal rubber seat, O-ring, or the entire vacuum breaker/backflow assembly. Seat replacement often stops slow weeps when the fixture body itself is sound.
• If the problem is repeated because hoses stay attached, install an anti-siphon vacuum breaker or a small pressure-relief device so the seal isn’t under constant stress when a hose is left connected.
• After replacement, test with brief pressure cycles and then simulate overnight pressure (if safe) to confirm the repair.

What Not to Do

• Don’t make leaving hoses attached and pressurized a permanent setup. That habit accelerates wear on seats and backflow devices.
• Avoid masking slow weeps with temporary wraps, tape, or sealants instead of repairing the failed seat or device. These fixes hide the problem and can cause larger failures later.
• Don’t force or over-tighten parts. That can damage threads and make future repairs harder.
• Call a pro when sustained pressurization causes repeated leaks or when replacement of the bib or backflow device seems necessary.

When to Call a Professional

• If you find corrosion or cracks in the bib body, or the backflow device is integral and damaged, a plumber should replace the whole assembly.
• If you’re not comfortable removing and bench-testing the backflow or seat, call a technician. Backflow devices may be subject to local code and must be installed correctly.
• If the leak persists after you replace the seat or device, or water is leaking into the wall, call a pro promptly.

Safety Notes

• Shut off the water supply before disassembling any valve. Sudden flow can cause injury or property damage.
• Work with the valve dry and use basic hand tools only. If parts are seized or corroded, avoid excessive force—stop and call a plumber.
• Backflow assemblies may be regulated. Do not discard or replace them without checking local requirements if you are unsure.

Common Homeowner Questions

• Q: Will replacing the washer fix an overnight weep?
  A: Often yes—if the seat or O-ring is the only worn part, replacing it usually stops slow weeps.
• Q: Can I leave a hose attached if I use a quick-disconnect?
  A: Quick-disconnects reduce the chance of debris but still leave the valve under pressure; it’s better to drain the hose or shut the shutoff inside.
• Q: Is the backflow device required?
  A: Many areas require an anti-siphon or backflow device; check local rules or ask a plumber before removing it.

More in this topic

For more related fixes and similar symptoms, see Outdoor Spigot Leaks Under Load.