2 ways to flush a hot water heater - which is better?

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M

MasterOfNone

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Location
Dayton, Ohio
Most places I've seen have said to flush a hot water tank completely once every year or 6 months. But I've also seen a few places saying to flush just a gallon or so once a month.

Which is better?

(I'll provide details about my own situation in a follow-up comment.)
 
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I’m a first-time homeowner since mid-2016.

My house’s previous owner (“Brian”) lived here for 6 years and wasn’t very handy but seems to have taken decent care of the place. The owner before him (“Mike”) was extremely handy and very attentive to all the infrastructure of the house, including the hot water heater.

Taped up by the workbench, I found a note from Mike to Brian with instructions to flush a gallon from the hot water heater once a month. (Apparently Mike cared enough about the house to give Brian those instructions even though Mike was moving out!) I have no idea if Brian followed the instructions exactly, but he probably flushed the water heater at least once every few years.

We’ve been here for about half a year and I have not yet flushed the water heater. (I only learned that I should a month or two ago.) So to reiterate the question, should I flush the whole thing and keep doing that once a year? Or should I flush a gallon from it once a month as directed by Mike?
 
Depends on how much scale build up your water heater produces. City or well water?
 
It's city water. Dayton, OH.

I'm guessing one big annual flush is better for when there isn't a lot of buildup? Or do I have it backwards?
 
Yikes! Did you put those pictures there to scare me?? ;)

It's a gas heater.

By the way, I'm also seeing conflicting advice for when I flush it:

- Some people say to turn off the cold water intake, some people say don't.
- Some people say open up a hot water faucet nearby, some people say don't.
- Some people say wait for the water to cool down, some people don't mention it.

Not sure whether there are specific cases where I should do one or the other.
 
OK, an update:

I drained the tank last night. Here's exactly what I did, in order. I think I did it right, you tell me:

1. Turned the dial to "Pilot"
2. Closed input valve
3. Hooked up a hose to the tank, with the other end stuck into the grate in my garage
4. Upstairs to open my kitchen sink (furthest from the water heater) all the way to hot
5. Back downstairs, opened the valve where the hose is connected to the tank
6. Listen for water rushing through (it felt like a lot lower pressure than I was expecting. Oh well) until it sounded empty or mostly empty.

7. Then I had my wife look at what was coming out of the hose in the garage while I turned the input valve on and off a few times (for about 10 seconds each time). This was the "flush." She said it looked like there was some sediment coming out, so that's good.
8. Then I thanked my wife kindly (very important!) and closed the valve where the hose was connected to the tank.
9. Opened the input valve
10. Turned the switch back from Pilot to On and listened for the whoosh of the flame lighting.
11. My wife turned off the kitchen faucet
12. Disconnected and put away the hose.
13. Tested, and we still had hot water later that night.

I think from now on, since we have hard water, I'm going to get the shortest length of hose I can find, so I can just flush a gallon per month into a bucket (the way Mike told Brian to!). If I do that, do I need to go through all the other steps?
 
I've honestly never shut water off to flush a tank and not sure why you would? I'm just curious who on the internet draws up these steps? Leave water on and open drain, let water run till water runs really clear, then a few more minutes. Thank wife kindly and put hose away.
Oh and Dayton typically has well water that is at 9 gpg and considered hard.
 
Deerslayer said:
I've honestly never shut water off to flush a tank and not sure why you would? I'm just curious who on the internet draws up these steps? Leave water on and open drain, let water run till water runs really clear, then a few more minutes. Thank wife kindly and put hose away.
Oh and Dayton typically has well water that is at 9 gpg and considered hard.
Click to expand...

You're not the first person who's said to leave the water on, but other people (including plumbers) have said to turn it off.
 
KULTULZ said:
Regardless, there is reason to completely drain the WH-

-Clean Sediment Out of Water Heater - Click Here-

This is for information only as to how and why. It makes perfect sense to me and is offered for information only.
Click to expand...

So the advice there is basically to drain the water heater twice; first with the intake turned off, and then with the intake turned on. That makes sense for once every 6 or 12 months.
 
MasterOfNone said:
So the advice there is basically to drain the water heater twice; first with the intake turned off, and then with the intake turned on. That makes sense for once every 6 or 12 months.
Click to expand...

It all depends on the total amount of sediments/contaminates in your water. The more contaminants you have, likely the more frequent draining you will have to do.

The first step is a total drain as described and maybe a quick flush in about six months to see the amount of sediment(s) that has settled at the bottom of the WH since the first drain.

And then there is de-scaling and sanitizing the WH.

Sediment(s)- Effect of On Wh.jpg

Gas WH Thumping - Sediment Buildup.gif
 
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Plumber's Guide #10 is correct; I am RH.
But, let me describe what I found with my 5 year old NG tank-type home water heater. The homeowner's manual that came with the new house recommends "draining" the water heater annually, and in fact the AO Smith instruction manual from that year also describes a draining procedure. I kind of slacked off in the first two years of ownership, then had a plumber I hire for jobs I don't have time to do drain the WH while he was here to work on another task in 2017. He also replaced the sillcock valve on the tank drain with a straight ball valve at that time. Since not much sediment came out in 30 minutes, I procrastinated until 2019, and had the same guy drain the WH while he was here to check the anode rod for the first time. Again, not much sediment in 30 minutes. Today, about 17 months later, I took charge of the "draining" myself. After about a half hour of draining, I was still getting a small but steady volume of mineral sediment out to the tank, as confirmed by holding a kitchen strainer under the hose output, so I opened the CW valve a little at first. When that caused heavier sediment to come out, I opened the valve all the way, and it was like a snowstorm coming out of the hose end. I had to let the system run wide open for another hour before the flush water ran clear. Tonight, I checked AO Smith owner manuals available on their Website, and found that they now provide instructions for "draining and flushing," instead of just draining. Although the new instructions don't describe flushing at full water pressure as long as I did, I believe that my episode was an anomaly, due to waiting too long between drainings, and inadequate draining procedures. I'm confident that the next drain and flush will take much less time (and water). So the point of my story is that draining alone is really not enough to completely remove what sediment can be removed in areas of hard water, like mine, especially with a home water softener, and flushing is a must (as the manufacturer now recommends).
 
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