Two years ago we got a local company to come in and install a new furnace, AC unit, and tankless water heater. It was pricey, but I'm hoping the products last a while. The comfort alone I think was worth it. These last few weeks have been around 30 degrees every day. The tankless hot water too a little getting used to since the cold water has to be flushed out of the lines before getting to the fixture, but knowing I'll never run out of hot water in the shower is worth the trade. When we do a renovation on the main floor I'm considering a home run plumbing system and that should help get the water to the fixtures slightly faster.

The maintenance is something that just kind of slipped my mind at first. When we got the water heater I skimmed the maintenance and it had some directions on draining it and such, didn't really think about it since. I asked one of the employees from the company who installed it and he said they don't really do much for maintenance on them. After some research during the home improvement boom of COVID-19 I saw some reputable youtube videos mentioning maintenance should be done on them every year or so, and this could mean the difference between a 7 year water heater and a 20 year water heater.

To a frugal guy like myself I thought this was a very big deal. I immediately purchased the equipment online once watching some videos on how to perform maintenance on my model.

Reason for the Tankless Hot Water Heater Maintenance Post

This may seem like an odd post for a software developer blog, but as I mentioned in my first post, this blog would also hold personal notes/experiences. This is DIY home maintenance that I will be performing every year to save money. I will be revisiting this post every year to lookup the steps as a reference.

Tools Needed

  • clean 5 gallon bucket
  • 6-8 liters of white vinegar
  • channel lock pliers
  • philips screwdriver
  • submersible sump pump with garden hose attachment
  • 2 washing machine hoses
  • garden hose long enough to reach laundry tub

Step One - Turn off the Gas to the Water Heater

The gas valve is located beside the water heater in my case. Turn the valve so it's perpendicular to the supply pipe to turn it off.

Natural gas pipe turned on.

Step Two - Turn the Power Off on the Water Heater

Press and hold the power button on the water heater itself to power down the unit. You can also unplug it at this time to ensure the power is off.

Step Three - Clean the Cold Air Filter

First, you need to remove the cover. There are 4 screws that need to be taken off to do this, 2 on the top, 2 on the bottom. Lift the cover up, there's a lip on the top. There's a screw on the front left of the cold air intake that needs to be removed that is attached to the filter. Then there's a screw on the front of the filter that needs to be removed before we can slide the filter out.

Use an old toothbrush to clean the filter out. Make sure the filter remains dry or you may get an error code on the water heater. Now reinsert the filter.

Step Four - Drain the Water Heater

There are both hot and cold valves located directly below the water heater. Turn off the valves to isolate the unit. Remove the caps on the service valves and hookup hoses to both the hot and cold service valves. Open the service valves and wait a few minutes for the tank to completely drain.

Step Five - Clean the Cold Water Filter

There's a filter by the cold water supply, it may require a channel lock to open, turning counter-clockwise. Make sure you have a bucket underneath to catch any remaining water. Clean the filter out with the old tooth brush. Reinsert the filter by hand, use the channel lock to give it another 1/8th of a turn.

Step Six - Clean Out the Dirt Trap

There's a pin that you pull straight out. Then pull the trap straight down. There's a O-ring for water sealing that needs to be intact. Clean out any debris in some cold water. Reseat the O-ring and reinsert the dirt trap.

Step Seven - Descale the Heat Exchanger

Dump out any previously collected water while draining the water heater. Add about 6 liters of vinegar to a clean bucket. Attach the cold water intake hose to the sump pump. Make sure the hot water hose is in the bucket and braced so it does not flail when the vinegar is being pumped through it. Plug in the sump pump and let it run for about 45 mins.

Step Eight - Flush out the Vinegar from the Water Heater

Turn off both service valves. Remove the hoses from the service valves. Attach a garden hose to the hot side service valve. Put the other side of the hose into the laundry tub. Leave the hot isolation valve closed. Open the hot service valve. Open the cold water isolation valve in order to push water through the system and out the hot service port into the laundry tub to flush all the vinegar out. Allow this to run for about 10 minutes.

Step Nine - Put Everything Back

Turn off all the ports first. Disconnect the garden hose. Place the service caps back on. Open the cold then hot isolation valves. Place the cover back on. Turn on the gas. Plug it back in/turn on the unit.

Then good til next year.


So I wrote all this before actually attempting it, and here are a few notes I have for next time.

Use a smaller container to catch water under the dirt trap, it was under some pressure it seemed.

There was a leak coming from the dirt trap after using some hot water. The o-ring needed to be removed and placed on the removable dirt trap before reinserting in order to be dirt free. It's not good enough to leave it in the unit when cleaning.

I didn't use a garden house because it was in use and I was too cheap to buy another one. Instead I used the cold water supply to flush the vinegar from the unit. I used the hot water service port to flush the vinegar into 2, 5 gallon pails. I did this 3 times to make sure all the vinegar was out.