Quick Answer:
After a city water outage you often have air and loose sediment in the pipes. Start by flushing air and sediment at sinks first, then retest the shower. If the shower flow is reduced, remove and clean the showerhead screens. If delays or low flow continue after those checks, consider calling a plumber.
Why This Happens
When the water supply is shut off and then restored, pressure changes push air and tiny mineral particles through the plumbing. Air pockets cause sputtering and delayed hot water as the system purges. Sediment and grit can briefly clog screens, cartridge valves, and thermostatic or mixing devices, slowing the appearance of hot water. Water heaters themselves can also be affected if their inlet sees a surge of debris, but most problems after an outage are in the distribution lines or fixture fittings.
Step-by-Step What to Do
Step 1 — Open a sink and flush air and sediment
- Choose a nearby sink (bathroom or kitchen). Open both hot and cold taps fully.
- Run water for several minutes until flow steadies and any sputtering stops. This clears air pockets and pushes out loose grit before it reaches other fixtures.
Step 2 — Repeat at other sinks
- Do the same at other sinks on the same floor, working toward the shower. Flushing sinks first helps prevent grit from reaching sensitive shower valves or cartridges.
Step 3 — Retest the shower
- After sinks are flushed, run the shower and observe how long hot water takes to arrive and whether flow is reduced.
- If hot water now arrives promptly, the issue was likely air or sediment that the sink flushing cleared.
Step 4 — Remove and clean the showerhead screens if flow is reduced
- Turn off water, unscrew the showerhead or use the removable spray arm. Inspect the small mesh screens and the inlet for grit.
- Rinse screens in clean water and wipe the inlet. Reattach and test flow again.
- If your shower has a built-in cartridge or filter, check manufacturer guidance before disassembling further.
Step 5 — Check the water heater and plumbing basics
- Make sure the water heater has power or the pilot light is on and that the thermostat is set to a normal temperature.
- If the heater is older or you notice reduced hot output across the house, sediment in the tank could be a longer-term issue.
What Not to Do
- Don’t keep cycling fixtures after an outage without flushing sediment—grit can damage valves.
- If delay persists, a plumber is appropriate; don’t try to force repairs on gas or electrical water-heating components if you aren’t trained.
- Don’t use harsh tools or excessive force on fixtures; most screens and cartridges are fragile and can be damaged.
When to Call a Professional
- Hot water still arrives very slowly after you flush sinks and clean the showerhead screens.
- Only one area or fixture shows a delay—this could indicate a local valve, cartridge, or cross-connection issue; see Delay only in one bathroom for troubleshooting steps that may point to a targeted fix.
- There is cloudy or sandy water coming from multiple fixtures, persistent low pressure, or signs of leaks. A plumber can inspect valves, pressure-reducing devices, and the water heater safely.
- If you recently had work done, or a remodel, and the problem started afterward, check the related fittings; a remodel can change the way the system balances—see Shower slow to heat after remodel for common causes.
Safety Notes
- Be careful when testing hot water—run water gradually to avoid scalding.
- Turn off power to an electric water heater before doing any inspection on the unit. For gas heaters, do not attempt gas repairs yourself.
- If you encounter rust-colored water, strong odors, or debris that won’t clear after flushing, avoid using the water for drinking or cooking until it’s tested or the supply is cleared.
Common Homeowner Questions
- Can air in the pipes delay hot water? Yes. Air pockets can interrupt flow and cause sputtering until they are flushed out.
- Will cleaning the showerhead fix slow hot water? It often fixes low flow caused by trapped sediment, but it won’t fix a problem inside the valve or water heater.
- How long should flushing take after an outage? Usually a few minutes per sink until the water runs clear and steady; larger houses or long runs may take longer.
For more related articles, see the Shower Takes Too Long to Heat Up hub.