Are You Killing Your Tankless Water Heater?

Tankless water heaters have been all the rage for nearly a decade now. They have become so common that it is rare for me to inspect a new construction house now that does not employ a tankless water heater. While these water heaters are energy efficient, they are not like your father’s water heater; these are high-tech appliances that require annual maintenance and servicing. Treating these water heaters like your old neglected hot water tank could significantly shorten the service life of this expensive equipment. Here is what you need to know.

Tankless Water Heater

The upside of tankless is efficiency, space saving, and unlimited hot water
Tankless water heaters are more energy efficient than conventional water heaters for two reasons:
1. They use high-efficiency burner technology that allows the appliance to extract almost all of the heat from combustion, this means there is very little waste heat venting from the appliance.

2. They also eliminate, “standing loss,” where a tank of hot water loses heat to the atmosphere. Combined, this makes tankless water heaters one of the more energy efficient ways to heat water.

Unfortunately, one of the upsides of these water heaters can also create a downside in efficiency: with unlimited hot water at your disposal, increased use of hot water can often offset the gains in efficiency.

In my mind, the best reasons to install a tankless water heater are space-saving and unlimited hot water. These appliances are much smaller than a 50-gallon tank and they can mount to a wall, allowing a closet space to be freed up for storage. If installed correctly, they should not run out of hot water, this can be especially important with a large bathtub.

The downside is maintenance and you need to have gas
Every owner’s manual I have read for these water heaters recommends regular scheduled cleaning of the heat exchangers. This is usually recommended annually, though, in places where hard water is common, more frequent descaling may be needed.

This photo shows scaling inside a heat exchanger

This photo shows scaling inside a heat exchanger

Cleaning a tankless water heater involves running vinegar or another approved cleaner through the heat exchangers to clean scaling and mineralization that can clog up the heat exchangers. These water heaters should be installed with a flush kit at the bottom of the water heater to allow the main water supply to be disabled so that a loop of cleaner can be pumped through the appliance. Some manufacturers of tankless water heaters sell corresponding full flush kits. The kits generally include a pump, some hoses, and a bucket.

This photo shows a flush kit for a tankless water heater

This photo shows a flush kit for a tankless water heater

Most homeowners are unaccustomed to servicing their hot water heaters. The old tank style heaters would certainly benefit from annual flushing and regular replacement of the sacrificial anodes that help protect the tanks from corrosion, but this type of regular, scheduled maintenance was seldom done on hot water tanks for a simple reason: replacement cost is relatively inexpensive.

You could quickly spend more maintaining these old tanks than they would cost to replace. The same is not true for these more expensive tankless systems. With replacement costs often in the $2500-$4000 range, tankless water heaters are well worth the investment of annual scheduled maintenance.

Can I run a tankless water heater on electricity?
They do make electric tankless water heaters, but in practice, these are not usually worth the effort. Tankless electric water heaters require a huge amount of amperage: often 125 amps for the models I have seen and many homes would require a whole new electrical service to handle these demands. In addition, the efficiency is not really there, making it difficult to justify the added expense. In practice, I do not see many electric tankless water heaters and probably for a reason. If you really want to go tankless and you do not have natural gas at your house, I would investigate a propane tank.

Tankless water heaters have a well-earned reputation for energy efficiency and space saving, but homeowners seldom think of the additional maintenance required. I always recommend to my clients that they have their tankless water heater cleaned and serviced on a regular maintenance schedule just like their furnace. This clearly reduces the cost-savings from these appliances, but hopefully, it makes them last and perform reliably. There is nothing worse than having your hot water heater suddenly die and I have noticed that appliances have an uncanny penchant for failing on national holidays when you have just invited your whole family over for dinner.
I hope this helps! Happy house hunting everyone!

Dylan Chalk

Author: Dylan Chalk

Dylan Chalk is the author of The Confident House Hunter – a book to teach home buyers how to look at and understand houses: Cedar Fort Press In June of 2017, Dylan's book The Confident House Hunter won the Silver Award from the National Association of Real Estate Editors. He is also the founder of ScribeWare inspection report software offering innovative and simple report-writing solutions - and he is the owner of Seattle-based Orca Inspection Services LLC. In early 2017 Dylan became the Vice-President of Western Washington chapter of (ASHI) American Society of Home Inspectors.