Last night I decided to blow air through my water lines to drain for winter. I started with the low point drain caps both off.I used the blow-out attachment to connect my compressor to my city water hook-up connection. I closed all taps, closed the fresh water tank supply hose, and opened my hot water bypass (closed my hot water feed valves, hot and cold, since my hot water drain plug is removed)Turned up the pressure and lots of air / water came out the cold water low point.Next, I closed the cold water low point and turned up the air pressure again.... My trailer just held the 60 psi of air pressure. I switched the position of the bypass valve and nothing changed.. I'm confused about what is happening. It appears like the bypass is not bypassing, but it allows water past during normal operation??? Am I missing something here or do I have some sort of blockage (ice, debris) that may be plugging up my air line enough to hold 60 psi back.

I never use the water heater by-pass. Just drain the water heater first and reseal it, then blow out the line farthest to closest front to back, then do each low point drain again. Also shoot some air thru the black tank flush if you have them. 60 psi is a little high, I use 45 psi. I thought the max psi from most trailers was 50 psi. Check your owners manual for you proper information. I have seen some water heater by-pass systems use two valves. I am not sure what you may have. No make or model in your post.

I don't know the layout of your piping. Maybe you have a check valve in there and you aren't blowing the line out in the correct direction.Also, I would use caution with an air compressor unless it is an oil less compressor. I don't think you are going to want oil in your drinking water.

69 Avion wrote:I don't know the layout of your piping. Maybe you have a check valve in there and you aren't blowing the line out in the correct direction.Also, I would use caution with an air compressor unless it is an oil less compressor. I don't think you are going to want oil in your drinking water.Check valve, interesting... I might have to search for that.Agree on the oil with compressed air, but it does not apply to me anyway. We don't use the fresh water for drinking since we don't treat the tank and lines to keep them safe. I tried air this year because in the past I've used antifreeze, and the smell never goes away. I still got antifreeze (very small amount, but still there) out when I blew the lines out last night. I have camped with this trailer all summer, and it is still coming out.I fear that I already have an ice block somewhere, it was minus 11 C overnight (12.2 F)after I returned from my last day camping on Sunday. When I got home I opened the low point drains and tilted the trailer, but the temperature got so low overnight that maybe I plugged them with ice already.

Yes, ice in pipes will hold air pressure. I would try to introduce water back into the system with the faucets open to make sure those supply lines are open. Probably best to do this on a warm day when temps are above freezing. Once verified that all are open, proceed with usual winterizing. One thing I do differently is to drain the system through the low point drains with faucets open before applying air pressure. The effect of a charge of water even under low air pressure hitting an elbow or closed valve can be enough to break things.

Why do people blow out lines instead of using $10 in pink stuff which assures that ALL of the water is out of the system. Correction: mine was $12 this year.

Blowing out water lines for winter storage. | Good Sam Community

40 Replies

Ex-Tech
Explorer
Oct 31, 2013
Just know that only blowing out the lines still leaves water in a few vulnerable places such as water pumps and ice makers.
doxiluvr
Explorer II
Oct 30, 2013
We do both. Blow out with air and run rv antifreeze through the lines and pour a little extra in the sink traps and toilet. We stored our TT outside in northern Wisconsin for 6 years and then this year it is in the high country of Colorado. Have had no prolems when de-winterizing in the Spring. I do think you should not use 60 psi as that seems sort of high for TT lines. Could cause damage to your lines.
DutchmenSport
Explorer
Oct 30, 2013
It is possible your water heater filled up with pressurized air and a check-valve somewhere in the line is holding the pressure. Why don't you try pulling the pressure relief valve on your water heater and see if air spews out. If it does, then somewhere you missed a valve to bypass the water heater. 60 psi seems awful high. I know each RV is different. The Keystone Manual say 30 psi.
BuckBarker
Explorer
Oct 30, 2013
Dick_B wrote:
Why do people blow out lines instead of using $10 in pink stuff which assures that ALL of the water is out of the system. Correction: mine was $12 this year.

'Cause it works. Except for the traps, I only used air when living in the mountains of AZ where it got below 0.
mark5w
Explorer
Oct 30, 2013
I do both. Blowout lines then use the antifreeze. I then leave all valves cracked half way. Why both. That's how I was taught on my first RV.
Dick_B
Explorer
Oct 30, 2013
Why do people blow out lines instead of using $10 in pink stuff which assures that ALL of the water is out of the system. Correction: mine was $12 this year.
westend
Explorer
Oct 30, 2013
Yes, ice in pipes will hold air pressure. I would try to introduce water back into the system with the faucets open to make sure those supply lines are open. Probably best to do this on a warm day when temps are above freezing. Once verified that all are open, proceed with usual winterizing.

One thing I do differently is to drain the system through the low point drains with faucets open before applying air pressure. The effect of a charge of water even under low air pressure hitting an elbow or closed valve can be enough to break things.
Nvr2loud
Explorer II
Oct 30, 2013
69 Avion wrote:
I don't know the layout of your piping. Maybe you have a check valve in there and you aren't blowing the line out in the correct direction.
Also, I would use caution with an air compressor unless it is an oil less compressor. I don't think you are going to want oil in your drinking water.

Check valve, interesting... I might have to search for that.

Agree on the oil with compressed air, but it does not apply to me anyway. We don't use the fresh water for drinking since we don't treat the tank and lines to keep them safe. I tried air this year because in the past I've used antifreeze, and the smell never goes away. I still got antifreeze (very small amount, but still there) out when I blew the lines out last night. I have camped with this trailer all summer, and it is still coming out.

I fear that I already have an ice block somewhere, it was minus 11 C overnight (12.2 F)after I returned from my last day camping on Sunday. When I got home I opened the low point drains and tilted the trailer, but the temperature got so low overnight that maybe I plugged them with ice already.
69_Avion
Explorer
Oct 30, 2013
I don't know the layout of your piping. Maybe you have a check valve in there and you aren't blowing the line out in the correct direction.
Also, I would use caution with an air compressor unless it is an oil less compressor. I don't think you are going to want oil in your drinking water.
Trail-Mate
Explorer
Oct 30, 2013
I never use the water heater by-pass. Just drain the water heater first and reseal it, then blow out the line farthest to closest front to back, then do each low point drain again. Also shoot some air thru the black tank flush if you have them. 60 psi is a little high, I use 45 psi. I thought the max psi from most trailers was 50 psi. Check your owners manual for you proper information. I have seen some water heater by-pass systems use two valves. I am not sure what you may have. No make or model in your post.

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Blowing out water lines for winter storage.

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