Drain moisture from air tanks

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Drain moisture from air tanks

June 14, 2013, 12:07:58 pm

David Whitehead mentioned to me today to drain the moisture from the air tanks as often as you think to do so, do not wait until "once per month" comes around. On the 2001, there are four valves, one in back and three in front, driver's side for rear one in front of rear wheel.

(The need to drain or blow the moisture out was discussed back in 2004 and 2005 but I do not see it recently. Just a reminder to Newbies.....the drier should remove moisture but some may still accumulate in the tank, especially that rear one, and you need to check it and let the pressure in the tank blow out the moisture. And if you see dust blow out, that is a whole different matter. At least that is what I have learned....hope it is right!)

Mike

Re: Drain moisture from air tanks

Reply #1 – June 14, 2013, 04:06:05 pm

I service my drier every 18 months as FT recommends and have never seen moisture in any tank. If I saw water at a drain, I would treat that as an emergency and get the drier serviced. Dust would indicate a catastrophe.

Re: Drain moisture from air tanks

Reply #2 – June 14, 2013, 04:20:13 pm

Yup, opening the air drains are basically a "report card" on the condition of the air dryer. If moisture or powder, service immediately.

If not, service every three years or so.

Re: Drain moisture from air tanks

Reply #3 – June 14, 2013, 04:33:31 pm

I service mine every 4 years .We put about 12,000 miles on a year and have never had any water drain from the wet tank.Gam

Re: Drain moisture from air tanks

Reply #4 – June 14, 2013, 05:06:49 pm

I drained my U295. But the other day I looked for the drains on my 40ft no tag 1999 U320 and could not find them.

Where are they?

best, paul

Quote

Yup, opening the air drains are basically a "report card" on the condition of the air dryer. If moisture or powder, service immediately.

Re: Drain moisture from air tanks

Reply #5 – June 14, 2013, 05:44:01 pm

If like my 2001, three tanks under front about under the chairs and on bottom of each is a valve that turn 90 degrees. The wet tank is in the rear with a valve that is on the bottom of the driver side front end of the wheel well. Call if that not work.

Re: Drain moisture from air tanks

Reply #6 – June 14, 2013, 06:34:38 pm

About a year ago, I found a bit of moisture and some "white stuff" when checking the "wet tank" via the drain valve at street side duals. Quickly scheduled a trip to NAC for service of dryer and other items. Have seen no moisture since. Fortunately, have not had any unusual issues with air systems. Had a bunch of leaks fixed in January, 2013. They seemed be more related to age than any problems from moisture or "white stuff."

On the 1997 U295, it's very easy to check the wet tank because the drain is plumbed to the valve in the wheel well. I plan to check that one monthly. The coach gets exercised at least every month. The two tanks in front require a trip under the coach to open the drains. I check those infrequently.

Re: Drain moisture from air tanks

Reply #7 – June 14, 2013, 09:44:21 pm

Quote from: J. D. Stevens – June 14, 2013, 06:34:38 pm

On the 1997 U295, it's very easy to check the wet tank because the drain is plumbed to the valve in the wheel well. I plan to check that one monthly. The coach gets exercised at least every month. The two tanks in front require a trip under the coach to open the drains. I check those infrequently.

Have you thought of moving those drains to the wheel wells also. Save some climbing under the coach.

Re: Drain moisture from air tanks

Reply #8 – June 14, 2013, 10:19:32 pm

Bingo!

It was a LOT easier to find and see on my U295.

Thanks, Mike!

best, paul

Quote

If like my 2001, three tanks under front about under the chairs and on bottom of each is a valve that turn 90 degrees. The wet tank is in the rear with a valve that is on the bottom of the driver side front end of the wheel well. Call if that not work.

Re: Drain moisture from air tanks

Reply #9 – June 14, 2013, 10:24:36 pm

Quote from: Barry Beam – June 14, 2013, 09:44:21 pm

Have you thought of moving those drains to the wheel wells also. Save some climbing under the coach.

Yup! I've considered it. I don't plan to move them. I'll be under there at least once a year checking stuff anyway.

If there is no moisture from the wet tank, there is little likelihood of moisture in the front tanks. On our coach, all the air in the front tanks passes through the dryer and the wet tank before it passes to the front tanks.

My understanding is that some of the newer coaches allow air from the 12VDC compressor to charge the front tanks. If that compressor charges the front tanks, "sumping" the tanks is more important. My understanding is that the drying system on the 12VDC compressor is not as effective as the dryer on the "big" compressor.

I check them about once a year and have never found any moisture, even when there was a bit of water and "white stuff" from the wet tank.

Re: Drain moisture from air tanks

Reply #10 – June 14, 2013, 11:19:51 pm

I moved my front tanks to valves on the wheel well as Barry or another noted. I wanted to check monthly and had been admonished, when buying, to not go working around under the coach. (That admonishment was later modified). Anyway, just FYI and only slightly related to this, the check valve or valves on the front failed, as some of you will recall, and my auxiliary compressor was (trying) to fill the large front tanks when clearly not intended to do so. I am not suggesting you could have this happen or to dissuade you from whatever schedule you want to follow, but after very considerable struggles we went thru with the dessicant and the moisture, I am probably a bit too sensitive.....still, I hope to help you avoid a problem be it ever so unlikely. It is just that David told me to check more frequently to be sure the condition was being maintained dry and I pass that on for whatever it is worth. Cheers folks, Mike

Re: Drain moisture from air tanks

Reply #11 – June 15, 2013, 02:05:43 am

I get moisture in the wet tank when the 120 volt AC compressor has been running for several days in a humid environment. I never get moisture when only the engine's compressor has been running, no matter how humid the weather. This leads me to believe that only the engine's compressor uses the dessicant canister. I haven't looked at the drawings to verify this, nor have I asked Foretravel. Does anyone on here know about this for sure? Maybe there's a second dessicant canister for the 120 volt AC compressor that I haven't found yet?

Re: Drain moisture from air tanks

Reply #12 – June 15, 2013, 06:13:10 am

rradio try the search. Use ,dessicant service awesome.Gam

Re: Drain moisture from air tanks

Reply #13 – June 15, 2013, 10:39:40 am

Quote from: RRadio – June 15, 2013, 02:05:43 am

I get moisture in the wet tank when the 120 volt AC compressor has been running for several days in a humid environment.

Do you mean the 12 VDC compressor is running occasionally over a period of several days to keep the coach level? If the 12 VDC compressor is putting air into the wet tank, the check valve to which Mike referred in a previous post may have failed. I think the 12 VDC compressor should not put air into the wet tank on a U300.

If your 12 VDC compressor is putting air into the wet tank, it may be running to keep up pressure throughout the entire air system. It probably has no effective drying system and will introduce moisture into the system. On our coach, the "main" air system will leak to zero pressure after several days. However, the leveling system usually does not leak. The 12 VDC compressor seldom runs. If all valves are working properly, the 12 VDC compressor never introduces air into any of the air tanks.

Re: Drain moisture from air tanks

Reply #14 – June 15, 2013, 12:57:53 pm

Quote from: J. D. Stevens – June 15, 2013, 10:39:40 am

Do you mean the 12 VDC compressor is running occasionally over a period of several days to keep the coach level?

On the '91 and earlier there is no HWH for leveling. Its a manual system using levers at the drivers seat that rotate the ride height valves.
Foretravel put a 3/4 hp, 120VAC compressor to keep the air up while parked. They did not put in any air dryer or even an air separator. I had my coach for 10 years that way before
I installed a separator with an automatic bleed valve but I do live out west were it's much dryer. I installed the dryer because I use it as shop air for cleaning things and didn't like the occasional droplets in the air.

Re: Drain moisture from air tanks

Reply #15 – June 15, 2013, 01:22:02 pm

John, Thank you for the clarification. I was not aware any coaches had 120 VAC compressors. Nor did I consider that the coach has hydraulic leveling. I spoke from my viewpoint of experience with the 1997 coach.

My education continues!

Why would one want to keep air pressure up while parked in the 1991 coach? I can understand that high pressure air would be handy as "shop air." Is the high pressure air required to operate anything on the 1991 coach while it is parked?

Re: Drain moisture from air tanks

Reply #16 – June 15, 2013, 01:25:50 pm

I sent a PM to JD because I thought he knew about this.....maybe? But I recall a thread a few days or week ago that mentioned a drier on the 12v compressor. Some had one, some did not and I could not figure how I do or should fit into that.

So to check, I looked on the back side of my 12v compressor and there is a glass bowl with what looks to be water in it but upon checking at a service company they told me those were condensate water drops in the bowl and I did not need to drain the bowl. I could not find a way to drain it, the bottom of the bowl has a white teflon or plastic fitting with some wires....no way I was going to take that off.

Sorry this may create confusion for some, to introduce this aspect. But I need to research later.....what is that glass bowl doing, where does the moisture go if I do not drain it out and if as the technician told me they would drain it if full, how do they do it? Hmmmm

By the way, I think a reply earlier made a statement that I might have misunderstood. I can only report on our coach the 12v does run to keep the coach level. That is why when leaving it stored we do not leave it in the level mode...the idea being to protect against a major air leak developing and causing the compressor to run excessively and burn up.

Re: Drain moisture from air tanks

Reply #17 – June 15, 2013, 01:40:03 pm

Mike, our aux compressor is similar and possibly exactly the same. The "thingy" on the bottom of the sediment bowl with the wires on it is a solenoid valve that opens when the compressor is off. It will allow the water to drain when it is open.

Twice in three years, I've pulled the valve apart and cleaned it. It tends to get junk on it that keeps it from closing securely. When that happens, the compressor does not effectively provide pressure for the leveling system while parked.

Re: Drain moisture from air tanks

Reply #18 – June 15, 2013, 01:46:03 pm

Quote from: Michael & Jackie – June 15, 2013, 01:25:50 pm

I sent a PM to JD because I thought he knew about this.....maybe? But I recall a thread a few days or week ago that mentioned a drier on the 12v compressor. Some had one, some did not and I could not figure how I do or should fit into that.

So to check, I looked on the back side of my 12v compressor and there is a glass bowl with what looks to be water in it but upon checking at a service company they told me those were condensate water drops in the bowl and I did not need to drain the bowl. I could not find a way to drain it, the bottom of the bowl has a white teflon or plastic fitting with some wires....no way I was going to take that off.

Sorry this may create confusion for some, to introduce this aspect. But I need to research later.....what is that glass bowl doing, where does the moisture go if I do not drain it out and if as the technician told me they would drain it if full, how do they do it? Hmmmm

Not sure if 2001 is the same as 2003.
That should be a N/O solenoid valve. When compressor is running it closes. When Aux air shuts off it opens the valve and expels accumulated water in the bowl and air up to check valve. If you have a desiccant bowl it would be next to this bowl.

Re: Drain moisture from air tanks

Reply #19 – June 15, 2013, 02:10:16 pm

Quote from: J. D. Stevens – June 15, 2013, 01:22:02 pm

Why would one want to keep air pressure up while parked in the 1991 coach? I can understand that high pressure air would be handy as "shop air." Is the high pressure air required to operate anything on the 1991 coach while it is parked?

Sorry, I guess I wasn't clear. The 1991(and earlier) Unihomes (U280, U300) have the same air suspension as the Unicoaches. But the air leveling is done manually. Foretravel cleverly mount the ride height valves on pivots. The levers next to the driver rotate the ride height valves (via a cable) and fool the ride height valves into raising and lowering the coach depending on the lever position. It's all mechanical, very simple and adds no extra valves or hoses. But it does need to maintain air in the system so that's where Foretravel added a 120VAC compressor, maybe there weren't good 12volt compressors available then?

Re: Drain moisture from air tanks

Reply #20 – June 15, 2013, 02:35:07 pm

Quote from: JohnFitz – June 15, 2013, 02:10:16 pm

The 1991(and earlier) Unihomes (U280, U300) have the same air suspension as the Unicoaches. But the air leveling is done manually.

Ah! You wrote "no HWH" and I inferred "hydraulic." Thanks for the further explanation.

Re: Drain moisture from air tanks

Reply #21 – June 15, 2013, 02:39:47 pm

I think I'm going to install a 12 volt DC compressor and keep my 120 volt AC compressor as well. When I'm plugged in I'll turn on the AC compressor and when I'm boondocking I'll turn on the DC compressor.

Re: Drain moisture from air tanks

Reply #22 – June 15, 2013, 07:59:14 pm

J.D. and Barry....THANKS. I wondered what that thing does/did. I think that explains a little stain on the carpet below that system.....looks like it was water. Wish the technician had told me it exhausts that water out from time to time! Thanks again for the explanation, makes sense even if complex versus a little manual drain.

mike

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