Quick Answer:
Turn off the outdoor water, open the spigot and inspect the underside of the deck while the faucet is running to locate the exact exit point. If you can access the fitting, remove nearby deck boards or an access panel to view the coupling, then replace a damaged freeze‑free riser or repair the penetration with proper flashing and insulation. Dry and treat any wet structural members before reassembly, and stop using the spigot until the leak is fixed.
Why This Happens
Water visible under the deck usually comes from the through‑deck penetration where the supply rises to the spigot. Common causes include a cracked freeze‑free riser, a loose coupling or packing nut, failed seal or flashing at the deck penetration, or freeze damage to the valve body. Water can track along joists and blocking so the drip may appear away from the actual break. Related problems you might see include Spigot sprays water under siding and Spigot leaks after winterization, which point to failed seals or freeze damage higher on the line.
Step-by-Step What to Do
1. Shut off the outdoor supply and confirm
- Locate the isolation valve for the outdoor faucet (inside the house or at the main shutoff) and turn it off.
- Open the spigot to relieve pressure and confirm water stops flowing from the supply side.
2. Operate the spigot while inspecting the underside
- With the valve off, have someone open the spigot while you watch the underside of the deck to pin down the exact exit point of the water.
- Note whether the leak comes from the riser, a coupling, or the deck penetration—a steady stream means a broken part; a slow drip suggests a seal or packing issue.
3. Remove nearby deck boards or access panels to view the coupling
- Carefully remove only the boards needed or open any existing access panel to expose the pipe and coupling.
- Use a flashlight and a rag to clean away dirt so you can see threads, nuts and seals clearly.
4. Minor fixes: tighten or replace packing and fittings
- If the leak is at a packing nut or threaded coupling and parts are accessible, you may be able to tighten or replace the worn packing or gasket.
- Use the correct replacement parts for outdoor, freeze‑resistant faucets. Re‑test before final reassembly.
5. Replace a damaged riser or repair the penetration
- If the riser is cracked, corroded, or the break is inside the deck structure, replace the riser with a proper freeze‑free unit or section of supply pipe.
- When re‑penetrating the deck, install proper flashing, a water‑tight boot, and insulating wrap where required to prevent future leaks and freezing.
6. Dry and treat any wet structural members before reassembly
- Use fans and dehumidifiers to dry joists and blocking. Remove any soft or spongy wood; treat salvageable wood with a wood preservative to inhibit rot.
- Only reinstall deck boards after the structure is fully dry and repairs are complete.
7. Reassemble and test
- Replace boards or close the access panel. Slowly restore water and test the spigot under pressure while watching the repaired area.
- Check again after a day of use to ensure no slow leaks were missed.
What Not to Do
- Avoid covering wet deck framing with new boards without repairing the source—this traps moisture and accelerates rot.
- Don’t ignore a leak or hope it will stop on its own; water will damage fast if left.
- Do not use open flames or improvised heat sources on wet wood to try to dry it quickly.
- Call a professional when the leak is inside the deck structure, you see structural rot, or the penetration requires rerouting the supply.
When to Call a Professional
- Call a licensed plumber if the leak is not accessible from an access panel or requires rerouting the water supply.
- Hire a contractor if you discover structural rot, widespread water damage, or if joists and decking need replacement.
- If freezing damage has broken a buried or hard‑to‑reach riser, a pro can safely replace and re‑insulate the run to code.
Safety Notes
- Shut off water at the isolation valve or the main before working on piping to avoid flooding.
- Turn off any electrical circuits if you must work near lights or wiring under the deck.
- Wear gloves, eye protection and a dust mask when cutting or handling treated lumber and when using preservatives.
- Avoid using torches or open flame to dry or seal areas—this is a fire hazard and can damage materials.
Common Homeowner Questions
- How do I tell if the freeze‑free riser is the problem? A visible crack in the riser, steady flow from the riser area when the spigot is opened, or moisture at the base indicate riser failure.
- Can I keep using the spigot until I fix it? No—stop using it. Continued use can worsen damage, flood the area, or cause rot that increases repair cost.
- How long before wet wood becomes rotten? Depending on conditions, wood can start showing mold and rot within a few weeks; dry and treat it as soon as possible.
More in this topic
For more related fixes and similar symptoms, see Outdoor Spigot Leaks Under Load.