Quick Answer:
If a backflow assembly starts leaking right after the system was restarted, stop the flow to that assembly immediately, relieve pressure, and check the device’s relief port and test cock positions. Small leaks from fittings can sometimes be tightened, but water coming from the relief port usually means the internal relief opened and should not be capped — call a pro if it doesn’t stop after basic checks.
Why This Happens
When a system is restarted there may be sudden pressure changes, debris moved by flow, or valves that did not return to the correct position. Any of these can force the relief to open or allow water to escape around seals and test ports. This is common after utility work or pipe repairs — for example, if Pressure unstable after city line repair or if sediment from work causes tripping of internal parts such as when Water discolored after pipe work.
Step-by-Step What to Do
Step 1 — Stop the supply
Find and close the inlet shutoff valve feeding the backflow assembly. If the assembly supplies a zone (irrigation, laundry, etc.), shut that zone off at the isolation valve. This limits further leakage and damage.
Step 2 — Relieve system pressure
Open a downstream faucet or a downstream test cock slowly to bleed pressure away from the assembly. Keep an eye on the assembly while pressure is relieved so you can see where water is coming from.
Step 3 — Inspect relief port
Look at the relief port area (normally a small vent or drain hole). If water is actively discharging from the relief port, it means the relief mechanism has opened. Clear any visible debris near the port so it can drain, but do not obstruct the port.
Step 4 — Confirm test cocks seated
Check each test cock (small screw-in valves used for testing). Make sure they are fully seated (closed) and not backing out. If a test cock is loose, gently snug it by hand or with an appropriate wrench — do not over-tighten.
Step 5 — Check external joints and unions
- Look for drips at unions, threaded fittings, and packing nuts.
- If a union is loose, hand-tighten and then give a small wrench turn. If a packing nut is wet, a small quarter-turn may stop a weep — avoid heavy force.
Step 6 — Contain the leak and monitor
Place a bucket or towel under the leak to protect surrounding areas. Re-open the supply slowly and watch whether the leak reappears or if the relief port discharges again. If the leak returns from the relief port or a test cock after the basic checks, stop and proceed to call a professional.
What Not to Do
- Don’t cap backflow reliefs.
- Do not disassemble the internal parts of the backflow assembly while the line is pressurized.
- Do not use sealants or temporary plugs on the relief port — these can create unsafe pressure and hide a failing device.
When to Call a Professional
- If water continues to discharge from the relief port after you have bled pressure and checked test cocks.
- If you find damaged internal parts, heavy corrosion, or if the assembly was submerged during a repair.
- If you are unsure how to isolate the device, or if the assembly supplies an essential service and you need a permanent repair.
Safety Notes
- Always relieve pressure before touching fittings or test cocks. Working on a pressurized backflow device can cause sudden sprays that may injure you.
- Wear eye protection and gloves when inspecting a leak.
- Never obstruct or plug a relief port — it is a safety feature designed to protect the system and water supply.
Common Homeowner Questions
Q: Can I cap the relief port to stop the leak?
A: No. Capping the relief port can create unsafe pressure and mask the real problem. It is not a safe or acceptable fix.
Q: If a test cock is dripping, can I tighten it myself?
A: Yes — a light hand or small wrench snug is acceptable for a weep at a test cock. Avoid heavy force; if it continues to leak, call a pro.
Q: Is water coming from the relief port a serious problem?
A: It often indicates the internal relief opened for a reason (pressure spike or internal failure). It’s a sign something needs repair and should be addressed promptly.