How and When to Flush Your Hot Water Heater

draining water boiler

How and when to flush your hot water heater used to be an easy question to answer for a plumber. Now, however, there are many different kinds.

1. Natural Gas Water Heaters

2. Propane Water Heaters

3. Electric Water Heaters

4. Power Vent Water Heaters

5. Green Water Heaters

6. On Demand Water Heaters in Natural gas, Propane, and Electric

7. Point of use Water Heaters

I think you get the point…

hands opening water heater

Each of these begs the question, “Do you really need to flush your hot water heater?” and if so, “How often should you flush your hot water heater?”

Let me answer the first question “Do you really need to flush your hot water heater?”

I know, you're thinking, "but my grandma's water heater lasted 20 years, and grandpa never cleaned it! This must be a sham!"

While it is true that there are always those water heaters that have outlived their "shelf-life" and have continued to operate like a champ in spite of the hard water, I can assure you there are hundreds more that did not.

If I had a nickel for every old water heater that I have pulled out of a crawlspace, by myself, with no help...

But I digress.

The Answer Is, Yes, You Do Really Need to Flush Your Hot Water Heater

Over time “crud” (also known as sediment and hard water) begins to accumulate in the bottom of your water heater. Now keep in mind we are going to be talking about tank water heaters, not on-demand water heaters just yet.

The tank water heater covers 1-5 above. Put a fan on it, it’s a tank water heater. Make it electric or gas, it's still a tank water heater.

You see, tank water heaters haven’t changed much since World War II.

In 1889 Edwin Rudd invented the automatic storage water heater. So, you can see that was a day or two ago.

And with all the technology in the world today, the average lifespan of a tank water heater is 12 years, while that of an on-demand is 25.

Tank water heaters are a lot shinier now than back then, and they have new terms like “eco-friendly” and “green technology,” but please remember, at the end of the day, the tank fills with water, the tank heats the water, and you use the hot water.

Just like in World War II.

(Side note: remind me to tell you the history of crawlspaces sometime.)

Anyway! The crud will settle in a couple of places. Most of the time, it sets on the bottom of the water heater and begins to accumulate.

In a gas water heater, the burner, over time, will have to heat the sediment that has settled in the bottom of the water heater before it even gets to the water, making it very inefficient.

hard water sediment in heater

In an electric water heater, the crud sets on the bottom and on the heating elements themselves. Eventually, the crud builds up enough that the two sides of the element touch and, boom! The element goes out, and your shower is now 10 mins. If you’re lucky.

If you're really lucky, your teenage daughter has just left her shower, and now it's your turn. Lol.

Regular Tank Water Heaters Should Be Flushed Once a Year

Now I can already see the eye rolls and the arm waves. It would seem as though someone ripped off an arm and beat you with it.

Relax. The process is easy.

  1. Turn off the electricity at the electrical panel (usually found in the garage or laundry room, or outside on older houses) for an electric water heater and turn the gas down to “pilot” on gas water heaters
  2. Turn the water valve off on top of the water heater (if there’s no shut-off valve, then turn off the main house water)
  3. Attach a garden hose to the drain on the bottom
  4. Run that hose somewhere you can effectively drain the tank (Tub, window, out the garage. you can also use a small pump to expedite draining)
  5. Open the valve on the drain
  6. Now open a sink or two only on the hot side (hots on the left, cold on the right)
  7. Let the water heater completely drain

(A note here on draining: If you can’t get any water out of your water heater, it may be plugged. If you cannot figure out a way to effectively clear it to get flow, call a professional. Having them unplug it is cheaper than replacing it before you were ready.)

  1. Now that the water heater is drained, just open the main water valve on top of the water heater. Let it run till water comes gushing out the hose end again, and quickly turn the valve back off.
  2. Repeat step 7 four or five times. This helps push the last bit out at the end.
  3. Close the drain valve at the bottom
  4. Open the water valve on top and let the tank begin to fill
  5. Remove the garden hose and get it out of your way (no one likes a messy work area, and be careful you don't slosh water everywhere)
  6. Leave at least one faucet open while filling. You will get a lot of air, and it will sound like a private jet trying to land, but it's ok. Wait until you have a consistent stream of water
  7. Turn off the faucet
  8. Turn your water heater electricity back on at the electrical panel or turn the gas back up to 120 (Note: some gas water heaters have letters. “A” would be 120 degrees. Some have lines with one longer red line. That is the line to set it to.
  9. Now wait a couple of hours for hot water

Now see. That wasn’t bad at all!

On-Demand Water Heaters Are a Different Beast

On-demands come in two kinds. Electric or gas (propane or natural gas).

worker opening water heater

Electric can be expensive to run, and gas has always been considered more efficient by most plumbing professionals.

But we aren't here to pick a new on-demand.

So back to cleaning.

For quite a few years, most companies wanted you to run vinegar through your on-demand heat exchanger (where the water is heated quickly) once a year.

After doing that for several years, they pushed it out to every two years, depending on the manufacturer. They found the vinegar was potentially harming the exchanger and even creating pinholes if cleaned too often. Otherwise, vinegar is exactly what you need (Note: CLR can also be used. Make sure to thoroughly read the manual for your unit before trying anything aside from vinegar)

A word of caution here. On-demands are not complicated, but it can be if you have never worked on one.

If you’re in any way uncomfortable, or if you pop the front off and think you're looking at a spaceship, seek professional advice. Many plumbing professionals are happy to walk you through the steps over the phone or a video call.

Now what do we do:

  1. Read your manual! I cannot stress this enough. Every unit or brand is different, and you must follow the cleaning procedure for that unit. Go cowboy on this one, and you could very well void the warranty.
  2. When in doubt, read number one.

When you finished following the procedures as laid out by the manufacturer, then you can re-fire the unit.

The nice thing about these is that you don’t have to wait. It's hot right now. Of course, these are more easily shut off when your teenager has worn out their half-hour shower welcome, and you're ready to get in.

Boy, if they only paid the bills...

But I digress.

We have touched on “What happens if you don't flush your hot water heater?” but I don’t think you're convinced. So let’s talk.

Everyone has seen the picture of the water heater that blows up from over pressuring. Amazingly enough, most people think that is because it wasn’t cleaned.

That’s Only Partly Correct

For one, the possibility of your water heater exploding is exceptionally small, I mean small, very small, so don’t worry about that.

A situation like that would only come from a complete lack of cleaning or maintaining, and the perfect storm of failed safety devices.

So don’t worry about it.

What should you worry about?

How about your wallet?

The first question that comes to mind for most people is, “How much does it cost to have your hot water heater flushed?”

Well, if you do it, just your time and a little sweat.

If you never clean it, then the tank crud will eventually eat through the tank and begin to leak.

Now you know water heaters only go out between one and four a.m. in the morning. Lol

When they do, they can do considerable water damage depending on where they are located in the home.

This is not to say they always just burst everywhere. Of course, you could get a pretty good leak, but that leak might have started as something small and grown.

Then there's the fact that most water heaters are never seen throughout the day.

Most water heater leaks, in my experience, were found by the owner's socks. Walking down the hall and then "squish" wet socks where the leak has finally made it into the main living areas.

Point is, it's cheaper to clean it than let it lay.

But what else can you do?

Let’s Take a Minute and Talk about Water Softeners

There are a lot of softeners on the market now. Literally thousands.

Why should you consider one?

tablets falling into water softener

Softeners remove a lot, if not most of the hardness from water. They almost make it soap-like, so those minerals don’t deposit themselves on the inside of your pipes, looking for their forever home.

This explains that "soft" feeling you get when taking a shower and wondering why you can never get all the shampoo out.

Also keep in mind that no system will remove one hundred percent.

What does this mean for your water heater.

It means that your cleaning will be easier and not nearly as frequent as those without a softener, due in large part to the fact nothing is sticking to the inside of your tank

In the case of on demand water heaters some warranties will not cover damage to the unit if you have bad water quality (in other words, the water is too hard)

Yes, I know, water softeners can be expensive, but like I said, so is a service call at 3 am when the tank finally gives out because hard water has eaten it from the inside out.

They never go out when it’s convenient.

It's ultimately up to you. You can get a salt softener all the way to a citrus based filter-softener. The sky is most definitely the limit when looking for water conditioning equipment

Now you’re asking yourself, “but Mike, which should I buy?”

Keep in mind we are here to talk about "how to" and "should you" clean a water heater. We will cover water softeners in another article.

For right now, focus.

Finally! Here We Are

We have talked about tank water heaters and how they are old 1889 technology, with an average lifespan of 12 years. We have talked about On Demand water heaters and how they are highly efficient, last up to 25 years, and are very convenient but need more maintenance because they have new technology.

We also talked about water softeners, their availability, their sensibility, and cost. I think we may have even hit, indirectly, of course, that it may just score some big points with the spouse in the house.

At the end of the day, just schedule yourself to do the cleaning. Jot it into your phone calendar or write it down on the fridge and give yourself a comfortable 4 hours to do it, but either way, make it happen.

Your wallet, your inner DIYer, and your spouse will thank you.