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Old 11-14-2017, 08:37 PM   #11
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Join Date: Dec 2016
Location: Southern California
Posts: 105
Originally Posted by CaptainVo View Post
Your plumbing is completely different than mine. I bet you could still just open up the hot water side of the sink and purge the tank with the air compressor.
Nope, that didn't work! I blew air into the system thinking all the water was out but on closer inspection I could hear bubbles burbling through the hot water tank when I turned the water pump on, and it sounded like there was a lot of water in there!

Here's a picture of my hot water heater tank from the inside. If you look at my diagram of the water lines, you can see these lines on the underside of the van. Cold water comes in through the bottom, and hot water goes out of the top. My theory is that air couldn't possibly push it out since since you can only push from the cold side and the air will just bubble up and go out the hot line (more on this later).

What I ended up doing was undoing the drain plug/rod from the outside of the water heater with a 1 1/16" socket (shown open on the very bottom of the picture). BE CAREFUL DOING THIS. The tank is pressurized and it nearly blew my fingers off when I undid it as the water shot out across the driveway. There's a ton of ?calcium deposits in there as well that acted as shrapnel. With this open, I blew more compressed air through the city hookup and a bit more water came out of the drain plug. With it open, the air pressure didn't reach the faucets anymore. I cleaned off an inch-thick layer of deposits from the rod and pulled what I could out from the tank with my finger. With the plug back in, blowing compressed air into the system will pressurize the tank again. I'm not sure if this is ok or not (see questions below). Remember to put a bit of teflon tape on the threads of the plug/rod. Hopefully any water that was inevitably left in the lowest parts of the lines was ok to freeze! I'll find out when I fill it back up.

Questions I have for the engineers (or plumbers) on here:

Is the hot water heater tank supposed to build up pressure or is that just cause I was blowing air into the system? How come it stayed pressurized with the hot water faucet open on the sink?

Is there a one way valve on the cold side (inlet) of the hot water heater tank so that the cold water can't flow backwards, and hence can't drain the tank that way? This is my best guess or else the hot water would leak out of the cold end with the cold water faucet open on the sink.

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Old 11-14-2017, 09:00 PM   #12
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Join Date: Jan 2012
Location: Western North Carolina
Posts: 1,258
That looks like very used up anode rod...
Time for a replacement.

2001 E350 PSD w/ a bunch of stuff.
And had three other E350s...
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Old 11-14-2017, 09:32 PM   #13
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Join Date: May 2016
Location: Pacific NW
Posts: 601
(I posted this before I saw your post #11. Looks like you discovered how pressurized water can turn an anode into a lethal projectile. Your anode is completely gone. Replace it.)

In order to maintain your water heater, you will need to drain and flush it, and remove and replace the anode on an annual basis. The purpose of the anode is to reduce the opportunities for electrolysis to damage the steel casing of your water heater.

There are numerous YouTube videos on how to do this. Here's a good one:

A few notes:

1. Be sure to de-pressurize your water system before you pull the anode rod, or the water pressure will blow it across the parking lot once you loosen the threads. Entertaining, as long as you aren't standing in front of the missile.

2. Most older RVs have not had the tank flushed and anode replaced for years. The last one I did, I needed to use a 3' cheater bar to get the threads to let go. Don't be surprised if you have to muscle it to get it to turn.

3. Be sure to flush out your tank. Invariably, they are loaded with stuff.

4. You will find both magnesium and aluminum replacement anode rods on the market. Aluminum lasts longer, but does not protect as well. Go with magnesium, and change it yearly.

5. Use thread tape on the threads of the new anode. It will seal better, and it will make it much easier to remove next year.

6. Once you have done it once, it is a very quick job.

7. I like to plumb a water heater bypass into my water system. This can be handy for maintenance, and for keeping water out of the water heater if you just want brief usage during cold weather, without needing to drain the water heater afterwards. There is lots of information online about water heater bypasses. Here's a couple of pics of one I did in my Roadtrek. The attached notes reference pink antifreeze--that's generally something to be avoided when possible, but cannot be avoided with Roadtreks.

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