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How to Clean & Flush a Tankless Water Heater
Tankless water heater cleaning removes mineral scale that builds up inside the unit as water passes through it. Central Illinois hard water makes regular flushing especially important because scale restricts water flow and reduces heat transfer. Homeowners with accessible service valves and the correct equipment can complete routine flushing by following the manufacturer's instructions.
Signs Your Tankless Water Heater Needs Flushing
Scale buildup changes how a tankless system operates. Signs that it needs cleaning include:
- Reduced hot water flow or pressure
- Water temperatures that shift between hot and cold
- Higher energy bills
- Error codes or warning lights
- Gurgling, banging, or whistling during operation
Water hardness varies across Illinois, with Central Illinois averaging 15-20 grains per gallon. Manufacturers typically recommend tankless water heater maintenance every 12-18 months, with more frequent flushing in hard-water areas.
If your unit is more than three years old and has never been flushed, schedule an inspection before attempting the first cleaning.
Tools and Materials Needed for a Tankless Water Heater Flushing
Check the manufacturer's manual before starting. You will need:
- A 1/4 HP or similar submersible pump
- Two 5-foot garden or washing-machine hoses with compatible fittings
- A clean 5-gallon bucket
- 2-4 gallons of undiluted white vinegar
- An adjustable wrench or pliers
- The manufacturer's manual for valve locations and restart instructions
This procedure requires accessible isolation and purge valves. If your system does not have them, professional plumbing installation can add service valves for future flushing.
Do not use bleach, harsh chemicals, or commercial descalers unless the manufacturer specifically approves them. The wrong cleaning product can damage internal components or affect warranty coverage.
Step-by-Step Guide to Flushing Your Tankless Water Heater
Follow the manufacturer's instructions for your specific unit if they differ from these general steps.
- Turn off the energy and water supply. Shut off the gas valve on a gas unit or switch off the circuit breaker for an electric model. Close the water supply to the heater.
- Relieve pressure. Open a hot water faucet, then locate the hot and cold purge valves on the heater.
- Connect the pump and hoses. Connect the pump outlet to the cold-water purge valve. Run the second hose from the hot-water purge valve into the bucket. Place the pump in the bucket with about four gallons of white vinegar.
- Circulate the vinegar. Open both purge valves and run the pump for 45-60 minutes. The vinegar circulates through the heat exchanger to loosen mineral scale.
- Rinse with clean water. Drain the vinegar, refill the bucket with fresh water, and circulate it for 5-10 minutes to rinse the system.
- Reconnect and restart. Close the purge valves, disconnect the hoses, and replace the valve caps. Restore the water and gas supply or electrical power according to the manufacturer's restart procedure. Run hot water to purge air, then check the unit and connections for leaks.
Common Mistakes to Avoid During Flushing
A missed step can create problems after cleaning. Avoid:
- Flushing without shutting off the gas or electrical power
- Skipping the clean-water rinse
- Overtightening hose connections or valve caps
- Using chemicals the manufacturer has not approved
- Waiting years between flushes in hard-water areas
- Restarting the unit without following the manufacturer's procedure
Hard water in Collinsville, Peoria, Springfield, and Bloomington speeds up scale formation. If flushing is followed by persistent tankless water heater error codes, stop resetting the unit and have the problem diagnosed.
When to Call a Professional Plumber for Water Heater Services
Call a professional when the heater has no isolation valves, error codes remain after flushing, or an older unit has never been descaled. Multi-unit systems, recirculating loops, and commercial equipment also require more involved service.
Professional water heater maintenance services provide inspection and descaling without requiring you to open or service the unit yourself. Annual professional maintenance extends equipment life and helps maintain warranty coverage.
If the unit has a failed heat exchanger or extensive damage, Tiger provides water heater installation when replacement is needed.
Why use Tiger Plumbing for Tankless Water Heater Flushing
Tiger is a family-owned home service provider that has served Illinois communities since 1993. Our licensed plumbers perform professional tankless descaling with commercial-grade equipment and manufacturer-approved solutions.
Tiger serves Collinsville, Peoria, Springfield, Bloomington, and more than 70 surrounding communities. From Springfield neighborhoods near Historic Route 66 to homes throughout the Peoria area, our team works with water heaters across Central Illinois. Check our service area for additional locations.
Check current plumbing deals before scheduling professional maintenance.
Tiger's HVAC technicians, plumbers, and electricians bring more than 30 years of home-service experience to plumbing, heating, cooling, and electrical systems throughout the region.
Contact Tiger today for expert tankless water heater flushing and maintenance across Illinois.
