When it comes to water heaters, there are many people who wouldn’t mind paying a few bucks extra if it would spare them the hassle of regular maintenance, so the term “self-cleaning” is very attractive. However, these types of short-cuts are seldom legitimate, no-strings-attached short-cuts, but they always cost more money. So, homeowners need to be careful before jumping at the idea of an uber low-maintenance water heater.
In order to determine if a self-cleaning water heater is worth the extra money, we need to know why water heaters require maintenance, the theory behind the technology or self-cleaning units, the effects of water hardness on sediment build-up, and how well self-cleaning water heaters handle hard water.
Self-cleaning water heaters are superfluous in areas with soft water. In places with moderately hard water, they may make enough of a difference to be worth the extra cost. Self-cleaning units will probably be overwhelmed by hard or very hard water and are unlikely to make enough of an impact long term.
Why Do Water Heaters Require Maintenance?
As you no doubt already know, the lifespan of a storage water heater depends a great deal on the quality of the water supply. In particular, water heater performance is influenced by the number of minerals as well as ‘total dissolved solids or TDS. TDS include dust particles and fine silt as well as larger bits of grit and gravel in the incoming water.
Unfortunately, however, there’s no getting around the fact that the process of heating water itself is largely responsible for the deterioration of water heaters (which is why you shouldn’t turn them all the way up). As the water heats up, it causes the formation of lime-scale—the whitish, chalky residue that settles on the bottom of the water heater.
This happens because the calcium, magnesium, and other minerals in water form solid compounds by reacting with the metal parts of the water heater, but only when the water grows hot enough to catalyze the reaction.
So, as a water heater performs its duties, two processes detrimental to its “health” are occurring:
- Corrosion of the water heater anode rod, heating element, and inner tank lining.
- Accumulation of lime-scale on the bottom of the water heater.
As the water heater ages, the lime-scale (also known as just scale) builds up and makes it difficult for the unit to heat water efficiently. This is especially true when the scale begins forming a coat over the lower heating element.
An older water heater with lots of scale build-up is very probably chowing a lot more power, trying to get the water heated to the desired temperature. Eventually, the built-up scale can cause the lower heating element or even the entire water heater to go bust.
Manufacturers recommend draining water heaters annually and de-scaling them every 2 years to prevent water heater failure that results from sediment and lime-scale build-up. More frequent de-scaling (once or twice yearly) is advised for areas with moderate to hard water (over 61 mg/l or 3.5 grains per gal).
If you’d like to read more on the effective draining of a water heater, check out this helpful post. For a step-by-step guide on de-scaling your water heater, you can read through DIY Water Heater Calcium Removal—Avoid 3 Costly Mistakes!
To find out how a self-cleaning water heater attempts to get rid of all the sediment and lime-scale that gets into it, read on!
How a Self-Cleaning Water Heater Works
Now, you might already have come across descriptions of how a self-cleaning water heater works. But, just to refresh your memory:
A self-cleaner has a curved dip tube (the tube that lets cold water into the water heater) instead of a straight one. Attached to the bottom of this tube is a small accessory that acts like an egg whisk. The pressure from the incoming cold water activates this “whisk”, stirring up the water at the bottom of the tank.
The purpose of this is to disturb the water enough that the grit, dirt, and lime-scale in the water can’t settle down at the bottom and exert their damaging effects on the tank. Instead, these solid particles are supposed to be pushed up into the hot water outlet and then out through your faucets.
If you were to opt for a self-cleaning water heater, then the fact that these particles are not removed before the water reaches your faucet can result in a definite difference between kitchen and bathroom water. This is because even though bathroom faucets are typically equipped with some kind of filter, kitchen faucet filters usually provide better filtration or have the option of installing additional filtration.
Manufacturers of self-cleaning units claim that these models reduce the frequency with which maintenance activities (draining, de-scaling, and flushing) need to be carried out. However, most makers still caution that homeowners do need to drain and flush out their water heaters “at least once every few years”.
The million-dollar question (well, two-hundred-dollar question, anyway!) is this: Do self-cleaning units really manage to stay free of sediment and scale build-up over long periods of time?
Water Quality and Sediment Build-up
As described earlier, when it comes to water heater performance, a lot depends on water quality. Particularly, the quantity of minerals dissolved in water (referred to as the ‘hardness’ of water) is responsible for the extent of scale build-up inside a water heater.
The table below provides a summary of water hardness classifications as per the USGS (United States Geological Survey).
| Water Hardness Classification | Mineral Concentration in ppm (mg/l) | Mineral Concentration in grains/gal |
| Soft | 0 – 60 | 0 – 3.5 |
| Moderately Hard | 61 – 120 | 3.6 – 7.0 |
| Hard | 121 – 180 | 7.1 – 10.5 |
| Very Hard | > 180 | > 10.5 |
In areas with soft water, even a regular water heater unit can keep chugging away even if it hasn’t been cleaned out in years!
On the other hand, in areas with moderate to hard water (upwards of 60 mg/l or more than 3.5 grains per gallon), a water heater might need de-scaling and flushing as often as once every 6 months. Even still, in spite of these efforts, folks that live in hard water zones might end up having to replace the lower heating element on their units every two to three years.
When a water heater runs only on soft water, it’s no biggie for it to continue functioning well. The problems arise when there’s hard water coming in, and worse still, when there are significant amounts of other solids, grit, dirt and so on, to deal with.
Naturally, the real test of a self-cleaning water heater’s “self-cleaning” efficiency is to check how well it performs in areas with hard water.
3. The Test: Water Hardness Effects on Self-Cleaning Water Heaters
Self-Cleaning Water Heater Performance (Poll Results)
Since there are no readily available figures for self-cleaning water heater performance in different parts of the country, I thought I’d piece together people’s experiences of using self-cleaning units from areas with different levels of water hardness, and use that as an estimate of how well these models are able to prevent scale from building up.
Polling friends living in different places who’ve been using self-cleaning units, I put together the info in a handy table.
| Geographic Region | Water Hardness Classification | Water Hardness Level | Scale Build-up |
| Thousand Oaks (California) | moderately hard | 119 mg/l | very little |
| South Jordan (Utah) | hard | 119 – 171 mg/l | some |
| Tucson (Arizona) | very hard | 211 mg/l | a fair amount |
| Idaho Falls (Idaho) | very hard | 239 mg/l | heaps |
Final Verdict on Self-Cleaning Water Heaters
Ultimately, the choice is up to you but based on the above information, I would say:
- Self-cleaning water heaters are not worth it if you live in an area with soft water because there is very little sediment build-up, even in regular water heaters.
- Self-cleaning water heaters may be worth considering for those who live in areas with moderately hard water.
- Self-cleaning water heaters are unlikely to make a significant difference to people who live in areas with hard and very hard water.