Annual flushing removes sediment that insulates the tank bottom from the burner (gas) or lower element (electric), reducing recovery rate and shortening tank life. Procedure is identical for all Reliance tank lines.
What you need
- Garden hose (long enough to reach drain or floor sink)
- Channel-lock pliers or wrench
- Bucket (catch initial sediment)
Procedure
- Turn off heat source. Gas: rotate thermostat dial to "Off" or "Pilot." Electric: flip breaker. Hybrid: set to "Off" via control panel
- Cool the tank. Wait 1-2 hours for water to drop below scalding. Alternatively run a hot tap for 5 minutes
- Close cold water inlet. Quarter-turn the cold supply valve above the tank
- Open a hot tap upstairs. Breaks vacuum, lets tank drain freely
- Attach hose to drain valve. Route to a floor drain or outside (downhill)
- Open drain valve. If plastic valve is stuck or won\'t open, see workaround below
- Drain 3-5 gallons initially into bucket — observe sediment color. Tank-bottom rust or chunks of calcium = good flush is needed
- Full drain. Continue until tank empties (15-30 minutes)
- Flush with cold water. Open the cold inlet briefly to stir remaining sediment, then drain again. Repeat 2-3 times until water runs clear
- Close drain valve, refill tank. Open cold inlet fully. Wait until hot tap upstairs runs steady (no air sputter) — tank is full
- Restore heat source. Gas: thermostat to "Hot" or 120°F. Electric: breaker on. Hybrid: select Hybrid mode
Stuck drain valve workaround
Reliance Standard tanks ship with a plastic drain valve that often seizes after several years. Options:
- Pliers + patience: work the handle slowly back and forth to break the seal
- Replace with brass ball valve: after first flush, replace the plastic valve with a ¾" brass ball valve ($15-20). Never sticks again. See Reliance drain valve part page
- Backflush instead: if drain won\'t open at all, run cold water backward briefly through the T&P valve to dislodge sediment (last resort)
Flush frequency
- Soft water: every 12-24 months
- Hard water (above 7 gpg): every 6-12 months
- Very hard water (above 15 gpg): every 6 months, plus consider a water softener
Hybrid Heat Pump flushing
HPHE-50 and HPHE-66 flush the same way as standard tanks. Additionally, clean the heat pump air filter monthly and check the condensate drain quarterly.
Mini-Tank flushing
SOMS 6-gal and 10-gal mini-tanks have a small drain at the bottom. Flush annually — disconnect inlet, open T&P, drain via the cleanout. Sediment accumulates faster on these due to small tank volume.
Bottom line
Flush annually (more often in hard water). Replace the plastic drain valve with brass after first flush. Combined with anode rod inspection every 4-5 years, tank flushing dramatically extends Reliance lifespan.