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Old 02-11-2013, 09:15 PM   #1
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Water Winterizing with Compressed Air

So I tried the compressed air technique for winterizing the water system in the SMB. I bought an adapter to hook a compressor to the city water hook up to blow out the system. I then pressurized the system to about 15 PSI and opened and closed all valves and faucets to try and purge the lines of water.

Here are a couple of comments:

Pressurizing the main tank did not seem to work, but not really sure. Maybe it is just too big to pressurize with my compressor.

It took more pressure and a lot longer time than I thought. 15 PSI just bubbled and gurgled interminably, but 20 to 25 PSI actually seemed to blow out the system. It took a LONG time to figure this out.

Remove the hot water anode and empty the hot water heater first, because the pressurized air seems to pressurize backwards through the cold water system. Somehow, the 8 gallon hot water tank seemed to have drained through the cold water side of the system.

After I blew out the system, I removed the anode from the hot water heater. The hot water tank was completely empty. (The anode was quite worn and corroded after less than one year).

I'm still not sure if the entire system is truly dry. I guess that is the advantage of using RV antifreeze. You can just throw it into the system and not have to worry about missing a line with the compressed air.
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Old 02-11-2013, 09:34 PM   #2
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Re: Water Winterizing with Compressed Air

Since city water systems can be 100 psi, I wouldn't hesitate to use 100 psi air to blow out the system.

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Old 02-11-2013, 10:15 PM   #3
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Re: Water Winterizing with Compressed Air

I looked at my compressor pressure gauge a little more closely and realized I was using closer to 30 to 35 PSI. That is probably about the minimum. I think the more pressure you use the more efficiently the air will blow out the lines.

I was reading in the SMB manual tonight (I know, guys aren't supposed to actually read the directions. . . ) and it said that the City water inlet actually has a pressure reducer. It didn't elaborate. Not sure what that would do.
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Old 02-11-2013, 11:49 PM   #4
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Re: Water Winterizing with Compressed Air

The water lines are rated at a max of 100psi, when I pressure test RV water systems I only pump them up to 40psi to find leaks. With an open valve at one end of your system, you will be pretty safe to blow it out at any psi. You should always use a pressure regulator on your hose when running the city water though, to bring it down to around 50psi. The city water inlet will bring the pressure down a little but it is mostly a check valve to keep the water from blowing back out when your using the water pump. Your fresh water tanks aren't air tight, they have a vent in the top of them, so that when the water pump is running it draws air into the tank. Other wise your tank would compress as the pump is pulling out the water and air. Which is why you couldn't pressurise it. When you are hooked up to city water, that line comes in after your water pump. The water pump itself has a check valve in it so the city water can't go backwards into your fresh water tank and can only go into your hot water heater and come out of your faucets.
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Old 02-12-2013, 07:28 AM   #5
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Re: Water Winterizing with Compressed Air

I have winterized many RVs this way and I never quite get ALL of the gurgling out of the lines. There is always trace water somewhere. If you are draining your hot water heater and blowing out the lines with decent air pressure (as mentioned above) you should be fine. I would add that I always leave any faucet open throughout the winter, and I relieve pressure at the water pump by disconnecting the line on one side or the other. Mine (and most I've seen) have quick connects there so I usually just leave it unhooked there for winter as well.

If your unit has an RV toilet, make SURE to get it completely cleaned out though. The valves in RV toilets are extremely fragile and are usually the first thing to freeze. They are about $50 bucks. Ask me how I know.

I'm not sure if SMBs are plumbed with PEX, but the stuff is pretty impressive, and with brass fittings you probably would never bust a line anyway unless you left the system fully pressurized.

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Old 02-13-2013, 09:06 PM   #6
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Re: Water Winterizing with Compressed Air

Quote:
Originally Posted by time2mtbike
The water lines are rated at a max of 100psi, when I pressure test RV water systems I only pump them up to 40psi to find leaks. With an open valve at one end of your system, you will be pretty safe to blow it out at any psi. You should always use a pressure regulator on your hose when running the city water though, to bring it down to around 50psi. The city water inlet will bring the pressure down a little but it is mostly a check valve to keep the water from blowing back out when your using the water pump. Your fresh water tanks aren't air tight, they have a vent in the top of them, so that when the water pump is running it draws air into the tank. Other wise your tank would compress as the pump is pulling out the water and air. Which is why you couldn't pressurise it. When you are hooked up to city water, that line comes in after your water pump. The water pump itself has a check valve in it so the city water can't go backwards into your fresh water tank and can only go into your hot water heater and come out of your faucets.
Thanks for the comments! I feel pretty good about the job the compressed air did blowing out the system.

After reading your post and thinking things through, I am guessing that the one place that definitely did not get blown out is between the water tank and the pump check valve. The SMB instructions recommend disconnecting the pump and draining it. I think I will take a look and see how much water is in there.
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Old 02-19-2013, 07:53 PM   #7
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Re: Water Winterizing with Compressed Air

Quote:
Originally Posted by edroid
Pressurizing the main tank did not seem to work, but not really sure. Maybe it is just too big to pressurize with my compressor.
The main tank has an overflow line that is always open to the atmosphere.

Also I use a shop vac and small piece of hose after removing the annode rod, replacement of which should be an annual event need-it-or-not.
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