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Gray tank vent


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#1 campnagle

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Posted 05 April 2009 - 08:17 AM

I vented my gray tank and this increases tank capacity by 8 gallons and cuts the dump time in half.
I used 1/4 MIP X 1/2 Barb fittings with 1/2 ID hose. Drilled with a 7/16 bit and tapped with 1/4 18 NPT pipe tap. Nice clean application.

Attached Thumbnails

  • vent_002.jpg

Edited by campnagle, 05 April 2009 - 11:16 AM.

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#2 Joe Z

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Posted 05 April 2009 - 11:41 AM

That's a real nice Mod.....
I must be getting brain freeze but what does the MIP mean?_____ and can these fittings be bought in Lowe's, Home Depot?________
I really like what you did there.
Joe

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#3 campnagle

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Posted 05 April 2009 - 12:10 PM

QUOTE (wrkn2mch @ Apr 5 2009, 11:41 AM) <{POST_SNAPBACK}>
That's a real nice Mod.....
I must be getting brain freeze but what does the MIP mean?_____ and can these fittings be bought in Lowe's, Home Depot?________
I really like what you did there.
Joe

MIP, male iron pipe. Any Lowes or home deep hole
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#4 Larry & Debbie Gamble

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Posted 05 April 2009 - 01:15 PM

Joe,
If you do the vent mod, remember on your '94 with the 13 gallon gray tank, it's located much further back. Your clear vinyl line must pass under two frame ribs on it's way to the vent T and will be about 20" long. You'll need to strap it up to prevent it from sagging. It will fill with water when you fill the tank to the top and then if it sags, it air locks and then ceases to be a vent. We had this problem on AZCharlie's and on mine. Charlie just unplugs his at one end to clear it when it occasionally clogs with water. I chose a different and more difficult path to solve mine.

Larry
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#5 dab

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Posted 05 April 2009 - 01:28 PM

I've seen other versions of this mod, where the tank was removed and the hole tapped at the top. It would seem that approach might yield more capacity, but certainly not nearly as easily. From a practical point of view, does it matter if the vent is at the side or on the top?

I need to do this mod AND get rid of the rubber p trap with the one way valve p trap mod.

Thanks.

Dave
Boise, ID

#6 Larry & Debbie Gamble

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Posted 05 April 2009 - 04:28 PM

Dave,
I've vented several on top but not to get more capacity. I did it for a combination vent/overflow and didn't route the line to the closet vent. I routed to the gray drain line, downstream from the valve. My take is that variation of the mod is more relevant to the old 13 gallon tanks when boondocking.
If the corner of the tank under the front step is elevated tight to the bottom of the Casita frame cross members, it is then the highest elevation of the tank and I think high in that side is plenty good. I do a layout that places the top of the fitting about 3/8" below the tank top. I've found most tanks to have about 5/16 wall thickness so that gets it close. To drop and reinstall the tank takes about an hour and a couple of 1 1/2" couplers to reconnect the two inlets as the tank is penetrated from both ends.

Larry
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#7 Joe Z

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Posted 05 April 2009 - 05:28 PM

Campnagle and larry.......... thanks and i will have to get under there and take a better look at it like you say larry i have to cross over some crossmembers so a drain valve inline on the way to the vent may be a quick cure on my 94'
Joe

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#8 kmfosterk

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Posted 05 April 2009 - 06:51 PM

QUOTE (dab @ Apr 5 2009, 03:28 PM) <{POST_SNAPBACK}>
I've seen other versions of this mod, where the tank was removed and the hole tapped at the top. It would seem that approach might yield more capacity, but certainly not nearly as easily. From a practical point of view, does it matter if the vent is at the side or on the top?

I need to do this mod AND get rid of the rubber p trap with the one way valve p trap mod.

Thanks.

Dave
Boise, ID


Dave I did the vent tube on top of tank and installed the Hepvo valve at same time. With the plumbing removed on the front end of tank I was able to drop the tank enough but did not need to remove it.

Attached Thumbnails

  • Vent_Tube.jpg

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#9 craig.humphries

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Posted 08 April 2009 - 12:33 PM

How does this mod increase capacity by 8 gallons and speed up dump time? No entiendo.
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#10 FakeHipBob

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Posted 08 April 2009 - 01:04 PM

This MOD effectively reduces the natural air block at the top of the tank. Some folks have seen increases of up to 15 gallons. This is adjusted because of the prior reduced capacity without the vent. The vent MOD also increases volume flow because of the lessening of the vaccum effect. I hope to get about 7 more gallons of storage out of my 16 gallon grey tank with this MOD.

Hope that helps.

Bob
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#11 craig.humphries

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Posted 08 April 2009 - 04:23 PM

Doesn't make sense to me, but what do I know? Are you saying that without this vent mod, people can only use somewhere between 1 and 7 gallons of their 15 gallon grey tank ... that over half the tank never gets used? Is this true for all Casitas, including my 2008?

What about the black tank?

If that's what you folks are sayin' then I'd better get this fixed asap. I'm no plumber, but I'm assuming my local Camping World can do the job.
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#12 Larry & Debbie Gamble

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Posted 08 April 2009 - 04:46 PM

Casita uses a system refered to in the plumbing world as a "wet vent". The pipe entering the tank not only allows air to escape from the tank as it fills, but also is the path that shower and bath sink water takes towards the tank. kmfosterk's photo reveals a drain that enters fairly high in the side of the tank. Not all Casitas are like this as it would appear that Casita hand drills the tank hole at the factory. Many are much lower. Once the tank fill to the top of the inlet pipe, no air can escape and the tank is full. When you factor in the wall thickness of the pipe, many Casitas cannot use the top 1 inch or so of tank capacity. Casita accommodates us by publishing a capacity of 25 gallons when in fact every late model tank I've removed had "capacity 33 US Gallons" stamped in the top of it. When you drain, it's slow at first, because your vent is full of water just like holding your finger over the soda straw. The vent availability increases as the tank drains. The revent mod cures the capacity issues and some folks, but not all, report increased drain speed. There are several additional restrictions to draining as well.



Larry

on edit:
craig.humphries,
You posted your second question while I was typing. You have a 25 gallon (acording to Casita) gray tank. Your FRESH tank is either 15 or 25 depending on which option you ordered. Early Casitas (pre '98 I believe was the switch over) had a 10 gallon gray tank that actually is stamped 13 gallons.

Edited by Larry & Debbie Gamble, 08 April 2009 - 04:52 PM.

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#13 Don

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Posted 09 April 2009 - 02:01 PM

Here are some photos of my blatant copies of the mods pioneered by Larry, Gene and Charlie.

Gray water tank vent - I took my vent tube into the closet and above the sink drain.
http://tinyurl.com/c7aj54
010.JPG .020.JPG

Gray water tank fast drain - BEFORE (12 min dump time) - AFTER (4 min dump time for greater amount of water)
http://tinyurl.com/dky6yg
030.JPG .040.JPG

Shower Valvectomy (Hepvo waterless trap) No more rubber P trap or manual valve!
http://tinyurl.com/asw8vn
050.JPG .060.JPG
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#14 campnagle

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Posted 09 April 2009 - 06:23 PM

Great pictures and instructions on the Hepvo waterless trap. From what I read the shower drains as fast and no back flow in shower pan but have read nothing about it keeping odors out. Also I assume it doesn't clog and you can simply unscrew it to clear? I have read no problems but am still a little shy on doing this. Also your part number is for the 1 1/4 but I see others done with the 1 1/2 ?

Edited by campnagle, 09 April 2009 - 06:31 PM.

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#15 KandJ

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Posted 09 April 2009 - 07:06 PM

This is an interesting thread.

If taping the tank and the vent pipe increases the capacity of the gray water and increases the dump flow, why doesn't Casita do it?

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