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Quick Answer
To flush a tankless water heater, you typically need 1 gallon of vinegar diluted with 4 gallons of water. This 5 gallon diluted vinegar solution is usually enough to flush out a standard residential tankless water heater. The exact amount can vary based on the size and capacity of your specific unit.
How Does Flushing with Vinegar Work?
Flushing a tankless water heater with a vinegar solution helps dissolve mineral deposits and sediment that can build up inside the heat exchanger and pipes over time. Here’s a quick rundown of the process:
- Combine 1 gallon of household white vinegar with 4 gallons of water to make your diluted cleaning solution.
- Turn off the power supply to the tankless water heater and shut off the water supply.
- Connect a hose to the inlet water line and place the other end in the diluted vinegar solution.
- Open the hot water taps in the house to allow the vinegar to circulate through the water heater.
- Let the vinegar solution run through the system for about 30 minutes.
- Flush the system with clean water to rinse out the vinegar.
- Turn the water and power back on.
The acetic acid in the vinegar dissolves mineral deposits like calcium and magnesium that can restrict water flow. Flushing with vinegar helps remove these deposits and restore proper water pressure and heating efficiency.
How Much Vinegar to Use
Most standard residential tankless water heaters have a capacity of around 3-5 gallons. Given this, a mixture of 1 gallon vinegar to 4 gallons water is usually sufficient.
Here are some guidelines for vinegar amounts based on tankless water heater capacity:
| Tankless Capacity | Vinegar Amount |
|---|---|
| 2-3 gallons | 1 gallon vinegar + 3 gallons water |
| 3-4 gallons | 1 gallon vinegar + 3-4 gallons water |
| 4-5 gallons | 1 gallon vinegar + 4 gallons water |
| 5-6 gallons | 2 gallons vinegar + 4 gallons water |
For larger capacity tankless water heaters, you may need to increase the vinegar to 2 gallons and dilute with 4 gallons of water.
The key is to use enough vinegar solution to thoroughly flush the interior components. If you have a larger home with multiple bathrooms, you may also want to use extra vinegar just to ensure adequate circulation throughout the plumbing system.
Flushing Frequency
How often you should flush your tankless water heater with vinegar depends on the hardness of your water and how quickly mineral deposits accumulate.
Here are some general guidelines:
- Soft water: Once every 2-3 years
- Moderately hard water: Once yearly
- Hard water: Twice yearly
- Extremely hard water: 3-4 times yearly
Symptoms that indicate it’s time for a flush include:
- Decrease in hot water flow rate
- Noisy heating operation
- Rattling or rumbling sounds
- High energy bills from inefficient heating
- Lime or mineral deposits visible on pipes or heater components
Flushing on a preventative schedule can help minimize scale buildup and keep your system operating efficiently.
Flushing Step-by-Step
Here is a step-by-step guide for flushing a tankless water heater using the vinegar method:
Supplies Needed:
- 1-2 gallons household white vinegar
- 4-5 gallons water
- Bucket or containers to mix solution
- Hose with fitting to connect to inlet water line
- Old towels or rags
- Goggles and gloves for safety
Step 1: Mix Vinegar Solution
Combine 1 gallon of vinegar with 4 gallons of water in large buckets or containers. Mix the solution well. Have extra water on hand if needed to top off.
Step 2: Turn Off Water and Power to Heater
Locate the shutoff valves for the cold water inlet and hot water outlet lines. Turn both valves clockwise to shut off water to the heater.
Locate the circuit breaker for the tankless water heater and switch it to the “off” position.
Step 3: Connect Hose to Inlet Valve
Attach a hose to the inlet valve on the water heater. Place the other end of the hose in the bucket or container filled with the vinegar solution.
Step 4: Open Hot Water Faucets
Open all hot water taps in the house – bathtubs, showers, sinks, etc. This allows the vinegar solution to flow through the plumbing system when the inlet valve is opened.
Step 5: Open Inlet Valve and Circulate Vinegar
Open the inlet shutoff valve on the water heater to let the vinegar solution flow in. Allow it to circulate through the tankless system and plumbing pipes for 30 minutes.
Step 6: Flush with Clean Water
After 30 minutes, close the inlet valve and then open the outlet valve to flush the vinegar solution out with clean water. Let the clean water run through the system for 5 minutes.
Step 7: Return System to Normal
Close all water fixtures and return valves to normal open position. Turn the power back on. The tankless water heater will take a few minutes to heat up again.
Check for any leaks and wipe up any spilled vinegar. Run hot water faucets to verify normal operation.
Flushing Safety Tips
When flushing a water heater with vinegar, keep these safety precautions in mind:
– Wear goggles and gloves, as vinegar can irritate eyes and skin.
– Keep children and pets away from vinegar solution.
– Make sure the room is well-ventilated.
– Avoid electrical hazards – turn off power at circuit breaker before disconnecting any pipes or hoses.
– Allow system to cool if it has been running so you don’t burn yourself on hot components or water.
– Have a bucket or towels ready to catch any water that drips.
– Read manufacturer’s instructions for your specific model. Some have special steps or requirements.
– Check with your local plumbing code authority if you have any concerns about the process.
Taking proper safety measures will help the vinegar flushing process go smoothly.
Signs It’s Time for a Flush
Don’t wait until your tankless water heater fails to flush it. Look for these signs it’s time for a vinegar flush:
– Hot water takes longer to get to faucets
– Decreased hot water flow rate
– Rattling or rumbling noises from unit
– High energy bills
– Mineral scale building up in pipes
– Cloudy hot water
– Foul sulfur smells in hot water
Regular flushing can help maximize efficiency and lifespan of your tankless water heater. Vinegar dissolves scale buildup before major problems develop.
How Long Does It Take to Flush a Water Heater with Vinegar?
The full process of flushing a tankless water heater using a diluted vinegar solution takes about 1 hour:
– 5-10 minutes to mix up vinegar solution and set up equipment.
– 10 minutes to shut off water, power, and connect hoses.
– 30 minutes for vinegar to circulate through system.
– 5-10 minutes to flush with clean water.
– 5-10 minutes to restore power and water supply, check for leaks.
Follow the vinegar circulation time recommended by your manufacturer. 30 minutes is often sufficient for residential tankless heaters. Bigger commercial units may require 45-60 minutes of vinegar to fully flush.
Proper setup, vinegar contact time, and clean water rinse are key to a successful tankless water heater flush.
Does Vinegar Harm Tankless Water Heaters?
Vinegar does NOT harm tankless water heaters when used properly for flushing. The diluted acidic vinegar temporarily softens mineral scale so it can be rinsed away.
Most tankless manufacturer manuals actually recommend periodic flushing with vinegar to descale the system. It’s often more effective and cheaper than chemical descaling products.
The key is diluting the vinegar properly with water – at least 4 parts water to 1 part vinegar. Undiluted vinegar could damage components.
Here are a few tips for safe use of vinegar when flushing:
– Dilute vinegar at least 4:1 with water
– Limit vinegar contact to 30-60 minutes
– Flush thoroughly with clean water after vinegar
– Don’t mix vinegar with other chemicals
– Check manufacturer guidelines for your unit
When used correctly, vinegar is a safe and effective way to flush tankless water heaters and keep them operating efficiently for years.
Conclusion
Flushing your tankless water heater regularly with vinegar is an essential maintenance task. For most standard residential units, a mixture of 1 gallon vinegar diluted with 4 gallons of water is sufficient. Flushing frequency depends on your water hardness and usage, ranging from every 2 years for soft water to 3-4 times per year for extremely hard water.
Pay attention for signs like decreased hot water flow, rattling noises, or mineral buildup indicating it’s time for a flush. The full process takes about an hour – mixing solution, circulating vinegar, and rinsing. Vinegar is safe for tankless heaters when used properly and helps remove scale buildup. Regular flushing can maximize efficiency and lifespan of your tankless water heater.