Tankless Maintenance Guide

Tankless water heaters make hot water available on demand, continuously until the valve is shut.

It is essential to understand nonetheless that just because it is energy efficient does not mean it is free of maintenance.

Actually, the more adequately preventive maintenance is done on the tankless unit, the surer its efficiency.

Please read our tankless maintenance guide below, together with estimated duration for each task.

The Rinnai tankless water heater installation requires both internal and external care, and majority of these tasks can be scheduled annually or as required.

Noting these tasks periodically on your calendar can help to make sure your tankless water heater unit functions at optimum efficiency.

Tankless Maintenance Guide: Exterior Maintenance

Clean the cover – 10 minutes

Use a cloth and non-abrasive cleaner to wipe the external part of the water heater unit from time to time so as to protect it against rust. Most especially in coastal regions where the metal can be damaged by salt accumulation.

Inspect the pipes – 10 minutes

In the cold season, check the pipe insulation for possible cracks and splits. Despite the pipes being protected from freezing by the insulation, it is advisable to reduce the amount of water supplied to the house in weathers below freezing temperatures.

Ensure that the drip runs as fast so as to continue without triggering on the unit.

Test the pressure relief valve – 15 minutes

This valve needs to be opened and shut to make sure it is functional. Turn the valve to release the hot water, and then ensure the flow stops when it is shut.

Trim around the unit – 15 to 45 minutes

If the water heater unit is placed outside, check the surrounding areas to ensure a clear space of 30 inches at least. Some people try to conceal the unit by planting trees or bushes around it, but a clear space provides clean air which is needed for combustion.

There is also the issue of reptiles being attracted to the unit from these surrounding bushes or trees which can enter into the unit, causing a fault. For a unit placed indoors, you still have to check to ensure this clear space is not blocked in any way.

Clean the air filter – 10 minutes

Some units come with a filter attached to the air inlet line which requires periodic cleaning, subject to the nearby areas (dust, lint from laundry room, pollen, etc.). Simply use a damp cloth to clean it.

Flushing out or descaling the unit – 1 hour

With hard water, flushing out or descaling the unit should be executed once in a year at least. You may be able to do this once in 3 to 4 years if you have soft water or an installed water softener in your home.

Even though it is not necessary to have isolation valves to flush out some tankless units heat exchangers, they provide a much easier option.

You will have to buy and install isolation valves if your tankless unit does not have one already. For proper flushing out of many tankless units, you will require a 5-gallon bucket, a small submersible pump (to circulate the flushing solution inside the bucket), and 2 hoses.

Tankless Maintenance Guide: Flush without isolation valves:

1. Shut the gas supply to the unit.
2. Shut the power supply to the unit, if necessary. (See manufacturer’s guide)
3. Shut the water supply (cold and hot) to the unit.
4. Detach the water connections (cold and hot) to the heater unit.
5. Connect a hose to the cold side from the outlet of the pump.
6. Connect a hose from the hot side into the bucket.
7. Position the pump in a 5-gallon bucket.
8. Pour white vinegar (3-4 gallons), or a solution recommended by the manufacturer, into the bucket.
9. Power up the pump and let it send the flushing solution into the water heater unit.
10. Allow this pumping and flushing through the water heater unit for about 45 minutes to an hour.
11. Shut off power to the pump and take it out of the bucket.
12. Detach the hose on the cold side.
13. Remove and wipe the inlet filter, then put it back in.
14. While the cold water supply is still shut, reconnect the regular connection cold water supply.
15. At this point you are about to rinse out the flushing solution from the water heater unit.
16. Ensure the hose from the hot water outlet empties into the bucket.
17. Gently turn on the cold water and allow it flush the unit for at least 5 minutes.
18. Shut the cold water and detach the hose from the unit’s hot side.
19. Reconnect the hot water line from the water heater unit to the house.
20. Turn on the gas. At this point, if you shut the power supply, turn it back on.

Tankless Maintenance Guide: Flush with isolation valves:

1. Shut the gas supply to the unit.
2. Shut the power supply to the unit, if necessary. (See manufacturer’s guide)
3. Shut both isolation valves and remove access port caps from each one.
4. Attach a hose to the cold side access port from the outlet of the pump.
5. Attach a hose to the hot side access port, with the other end emptying into the bucket.
6. Position the pump in the bucket.
7. Pour white vinegar (3-4 gallons), or a solution recommended by the manufacturer, into the bucket.
8. Open the valves of the access port.
9. Power up the pump and let it send the flushing solution into the water heater unit.
10. Allow this pumping and flushing through the water heater unit for about 45 minutes to an hour.
11. Shut off power to the pump and take it out of the bucket.
12. Shut the cold side access port valve, detach the hose and put back the cap.
13. At this point you are about to rinse out the flushing solution from the water heater unit.
14. Ensure the hose remains attached from the hot water access port and emptying into the bucket.
15. Gently turn on the cold water and allow it flush the unit for at least 5 minutes.
16. Shut the valve of the hot water access port, detach the hose and put back the protecting cap.
17. Now, turn on the hot water isolation valve.
18. Turn on the gas. At this point, if you shut the power supply, turn it back on.

Tankless Maintenance Guide: Interior Maintenance

Clean the burner assembly

Subject to the nearby environment (such as areas with salt water or pollen), cleaning of the burner assembly may have to be done more often than once yearly.

Please note that we do not provide guidelines for cleaning the burner assembly of your tankless heater unit. As the well being of our customers is paramount to us, this task must be carried out by a licensed plumber.

Please read our article on Tankless Buying Guide