Leave tank drain open after antifreeze? - Fiberglass RV

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Old 01-01-2016, 01:54 PM   #1
Name: denny
Trailer: 2001 Scamp 16 layout 3
Posts: 42
Leave tank drain open after antifreeze?

Winterized trailer with antifreeze in water tank. Pumped it thru sink faucet and drain and it drained into and out of the grey tank. Then I opened the fresh water tank to drain as much as possible that the pump left in the tank (still has a tad that would not drain out the drain valve). Now do I close the tank's drain valve or leave it open? If left open will it dry out the tank to prevent mold? Will spiders/other crawl inside? If close it won't that result in the leftover water/antifreeze producing slime and mold? Trailer will sit till Spring. What should I do?

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Old 01-01-2016, 01:59 PM   #2
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Name: Bob
Trailer: 1973 Hunter Compact II
Posts: 7,912
As there should already be an air vent that can't be closed, I always close the drain valve just so that I don't get my feet wet when I refill the tank.

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Old 01-02-2016, 11:09 AM   #3
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Name: Gordon
Trailer: 2015 Scamp (16 Std Layout 4) with '15 Toyota Sienna LE Tug
North Carolina
Posts: 2,309
I doubt you can get the tank and lines completely dry as a method of preventing contamination. If you could get ALL the water out then you would not have to winterize. The drain valve and tank are not designed to completely drain the tank, let alone the plumbing. You might get close using compressed air however.

According this this web site, RV antifreeze in the proper mix does have some ability to prevent tank and plumbing contamination. But if the concentration is too low it actually encourages the growth of microbes.

In addition, RV antifreeze lubricates the plumbing and helps to prolong the life of seals.

So, concerns over wet feet aside, it probably makes little difference if the drain is open or closed during winter storage. I would close it just to keep insects out.
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Old 01-02-2016, 12:47 PM   #4
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Name: Wayne & Barbara
Trailer: Parkliner
Posts: 709
Keep RV antifreeze in the tank with drain closed.

When you are ready to flush the A/F out in the spring, you can get more of it out by tilting the tank toward the drain. Do that with the hitch jack. either up or down , whichever does the job. Open the drain then flush remaining A/F with numerous small amounts of fresh water. Close the drain, level the trailer, fill the tank, turn on the pump, and flush the lines and water heater. Finally, drain the grey and black water tanks.
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Old 01-03-2016, 07:19 PM   #5
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Name: Darral
Trailer: Scamp Standard 13' 2010
Posts: 1,523
I never leave my valves open...period!
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Old 01-04-2016, 06:19 AM   #6
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Name: Donna D
Trailer: Escape 5.0 TA, 2014
Posts: 24,540
Lots of folks have put deck plates in fresh water tanks so they can thoroughly dry and sanitize those tanks. Of course you have to be able to get to it and that depends on the build. Little House Customs sells a cap that replaces the drain caps for the black and gray tanks and has a screen to keep critters out, that allows those tanks to dry out. Something to consider.

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Ten Forward - 2014 Escape 5.0 TA
Double Yolk - 1988 16' Scamp Deluxe
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