What chemicals can you use to clean a tankless water heater?

Tankless water heaters, also known as on-demand or instantaneous water heaters, provide hot water without the use of a storage tank. Instead, they heat water directly as it flows through the unit. This allows them to provide an unlimited supply of hot water on demand without running out like a conventional storage tank water heater can.

While tankless water heaters are very convenient, they do require regular maintenance to keep them operating efficiently. Over time, minerals from the water can build up and clog the internal components. Flushing the tankless water heater to remove these mineral deposits is an essential part of the maintenance process. When flushing, special care should be taken to use the right chemicals and cleaning solutions to dissolve the deposits and sanitize the system without damaging the heater.

What causes mineral buildup in tankless water heaters?

Hard water is the primary cause of mineral deposits and sediment buildup in tankless water heaters. Hard water contains high levels of dissolved minerals like calcium, magnesium, and silica. As the water is heated inside the tankless unit, these minerals precipitate out and accumulate on the internal components.

Some of the problematic minerals include:

– Calcium carbonate: Forms limescale deposits
– Silica: Leads to glassy scale buildup
– Magnesium: Creates hard mineral deposits

Over time, these mineral deposits restrict water flow and reduce the efficiency of the heat exchanger. This can lead to a number of problems such as:

– Increased energy consumption and higher utility bills
– Failure to reach the desired outlet water temperature
– Eventual damage to internal components
– Complete blockage of water flow requiring replacement of parts

Regular descaling and mineral removal is necessary to combat mineral buildup and keep a tankless water heater working properly.

How often should you flush a tankless water heater?

Most manufacturers recommend flushing a tankless water heater annually to prevent excessive mineral buildup. However, the actual flushing frequency depends on several factors:

– Water hardness – The harder your water, the more often you need to flush the tankless unit. With extremely hard water, flushing may be needed every 6 months.

– Water usage – Homes with high hot water usage will need to flush more frequently than homes that use less.

– Age of system – Older heaters are more prone to mineral accumulation and require more frequent flushing.

– Water quality – Well water or groundwater often has more contaminants that can clog a tankless unit.

– Manufacturer recommendations – Each brand provides specific guidelines on maintenance schedule.

– Symptoms – If you notice changes in hot water flow, temperature fluctuations, or error codes, it’s a sign to flush the tankless heater.

In addition to annual flushing, a tankless water heater should be descaled regularly to break down existing mineral deposits. Citric acid-based descalers are commonly used for this purpose.

What methods can be used to flush a tankless water heater?

There are three main methods used to flush and descale a tankless water heater:

1. Manual flushing: This involves an isolation valve kit and garden hose to flush the unit manually. The process sends a high-velocity stream of water through the tankless heater to remove loose sediment and buildup. A pump can also be added to increase water pressure.

2. Tankless water heater flush kits: These kits include adapters, tubing and a pump to connect to the hot and cold lines on the tankless unit. Flushing solution is then recirculated through the heater and out the drain. Kits allow an easy DIY flush.

3. Professional flush service: A technician will isolate the tankless heater, connect it to a descaling pump truck, and recirculate an industrial descaling solution. This provides a thorough flush but is the most expensive option.

The manual method or a flush kit is suitable for annual maintenance flushes. But a full professional descaling service may be recommended for heavily scaled units.

What chemicals are best for cleaning tankless water heaters?

The right chemicals are critical for an effective tankless water heater flush. Chemical cleaners help break down mineral deposits and sanitize the system. Some options include:

Citric Acid

Citric acid effectively removes scale buildup and is suitable for regular descaling. It breaks down calcium carbonate deposits. A 20% citric acid solution is recommended.

Vinegar

White distilled vinegar makes a good mild cleaning solution. It helps dissolve lime and calcium scales. Use up to 50% vinegar mixed with water. Avoid prolong contact with stainless steel.

Phosphoric Acid

Phosphoric acid-based cleaners quickly dissolve limescale and rust deposits. It is stronger than citric acid solutions. Use caution and follow manufacturer instructions.

Sodium Bisulfate

This acidic salt removes heavy mineral scaling and corrosion. It is effective for older units with excessive buildup issues. Use proper safety gear when handling.

Hydrochloric Acid

Hydrochloric acid works well removing stubborn scale deposits but can be highly corrosive. Take precautions when using and never use on stainless steel components.

Enzymatic Cleaners

Enzyme-based cleaners use bacteria cultures to dissolve organic contaminants and biofilms. They help clean out sludge and bacteria from the system.

Antimicrobial Agents

Antimicrobial cleaners kill bacteria and sanitize the system after flushing. They prevent biofilm re-growth and odor issues. Common examples are bleach or peroxide cleaners.

Step-by-Step Guide to Flushing a Tankless Water Heater

Follow this step-by-step process to properly flush a tankless water heater:

1. Turn off power and water supply to the tankless unit. Open hot water taps to depressurize lines.

2. Disconnect inlet and outlet water connections. Attach garden hose fed from water supply to inlet port. Attach drain line to outlet port and direct it to a drain or bucket.

3. Prepare cleaning solution according to manufacturer recommendations. Citric acid or vinegar-based descalers are commonly used.

4. Connect pump if available. Make sure incoming water supply is turned on.

5. Run the cleaning solution through the tankless heater for 15-20 minutes. Check the outlets to ensure solution flows freely.

6. Rinse out cleaning solution by flushing with fresh water for a few minutes to wash out any residue.

7. Reconnect hot water supply line to inlet and cold water line to outlet. Turn on water supply and power on unit.

8. Open hot water faucets and run for 5 minutes to purge air and flush residue.

9. Check temperature and flow to ensure normal operation. Unit may need to run through a de-scaling cycle.

10. Inspect external filters/strainers and clean out any debris. Replace if worn.

Following proper flushing procedures helps remove scale deposits and maintain a tankless water heater for optimal performance. Regular descaling prolongs the life of the unit.

Precautions When Flushing a Tankless Water Heater

It’s important to take safety precautions when flushing a tankless water heater:

– Turn off power to the unit at the breaker before starting. Verify it’s powered down.

– Allow the unit to cool before flushing if recently used. Flushing while hot can damage components.

– Wear eye protection and gloves when handling cleaning chemicals. Follow usage directions.

– Check cleaner compatibility with your tankless heat exchanger. Incompatible chemicals can corrode the exchanger.

– Never mix cleaners together as toxic gases can form.

– Avoid hydrochloric acid with stainless steel heat exchangers.

– Rinse out cleaners thoroughly with fresh water when done.

– Check for leaks at water connections before turning water supply back on.

– Never operate the tankless heater without water flowing through it to prevent damage.

– Clean up any descaler spills immediately to prevent corrosion of plumbing lines or surfaces.

– Flush only when mineral buildup is suspected or at recommended intervals. Over-flushing can erode components.

Following flushing best practices ensures the tankless water heater is properly maintained without causing premature wear or failure. Consult the manufacturer or local plumber if unsure how to properly flush the unit.

Signs It’s Time to Flush Your Tankless Water Heater

Some signs that indicate it’s time to flush your tankless water heater include:

– Decreased hot water flow – Clogged heat exchangers reduce flow rate.

– Slow heating or failure to reach desired temperatures – Mineral scales insulate heating elements.

– Higher energy bills – Scale buildup reduces heating efficiency.

– Strange noises – Scaly deposits cause vibration and noise during heating.

– Discolored or stained water – Rusty or dirty water indicates sediment in lines.

– Error codes – Codes related to overheating, flow restriction, or ignition failure.

– Older unit age – Heaters over 3-5 years old likely need descaling.

– Hard water – With over 10 grains per gallon of hardness.

– Bad odor from hot water – Bacteria growth in the unit causes foul smells.

– Long waits for hot water – Deposits in the heat exchanger slow response time.

– Need to flush frequently – Having to flush more than once a year signals a problem.

If you notice any of these warning signs, it’s definitely time to descale and flush your tankless water heater. Catching buildup issues early makes flushing easier and prevents damage.

Conclusion

Regular flushing and descaling is critical to keeping a tankless water heater operating at peak efficiency and prolonging its lifespan. Allowing mineral scale buildup to go unchecked can lead to reduced performance, increased energy usage and repairs down the road. Following an annual maintenance schedule and using the right chemical cleaners for your particular unit will keep it working properly for years to come. Watch for the telltale signs of scale buildup and flush the tankless heater before major problems occur. With proper care, your tankless hot water heater will provide reliable service and hot water on demand.