Once again ----- toilets (1 Viewer)

Jan 8, 2013
8,478
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Dronfield - Derbyshire
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Can someone explain how the vent valve works on my C400 cassette?

There's a pivot and valve over a spring and a piece of plastic hanging at the other end inside a tube that somehow has to operate it.
How?
Why?
Do I need one ---- or shall I just blank it of?

Items 22 to 39

upload_2018-4-26_16-55-47.png
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
52,700
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On the coast in West Sussex
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658
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Hymer B678 DL
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Since 2008 & many years tugging
I assume it's the over pressure vent valve you are talking about. I wouldn't blank it off as it releases any pressure build up in the tank, important if you like driving over mountains.
Old cassettes never had one I found out the hard way. Years ago in the caravan cassette had been emptied before the journey home, little daughter asked if OK to use the loo as she was desperate. Anyway I forgot she had used it then a couple of weeks later thought better clean up the loo, unknown to me she had done a number 2 and there were no chemicals in the cassette. I opened the slide there was a big whooph and I had a face covered in sh*t.
 

pappajohn

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Aug 26, 2007
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Far too complicated for a simple vent.
Is it to allow air to enter when emptying in the same way the older cassettes had a push button ?

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OP
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Stealaway
Jan 8, 2013
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I'm sure pappajohn is right, it seems so complicated and I'm seldom in any mountains.
Without it the valve is permanently open and you can't control the emptying flow with the button.

What makes it open?
How can excessive pressure do it?
You would think it would push the valve against its seat even harder. Parts 26-28[/QUOTE]
 

WSandME

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Aug 9, 2016
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From memory, I think the valve remains open (when in place - as the seat mechanism opens the valve) to equalise pressure. There is a foam flotation device to reseal it if the contents reach it.
 
Apr 10, 2010
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Since Sept 2003
It's a valve that is operated by a 'bump' on the base of the housing. When the cassette is slid into place the 'bump' pushes the plastic rod up, which rocks the valve down and open, rather like the old-fashioned push rod and rocker in the cylinder head. The value closes when the cassette is extracted.

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Stealaway
Jan 8, 2013
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From memory, I think the valve remains open (when in place - as the seat mechanism opens the valve) to equalise pressure. There is a foam flotation device to reseal it if the contents reach it.

I think you've got it - by god he's got it.
That's what the hump does, so it opens when the cassette is pushed in!

Brilliant - Thank you very much
 
Jul 5, 2013
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If you look under the panel on the floor of the cassette housing the one with the bump on it you might have a filter and a fan we do.
Cliff
That is the Thetford version of a SOG. You know you have it if the first push of the flush button starts the fan which can be heard running.

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Stealaway
Jan 8, 2013
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That is the Thetford version of a SOG. You know you have it if the first push of the flush button starts the fan which can be heard running.


No fan, no switch, just a 30mm diameter piece of flexible hose out the bottom of the van.

If I can fit a bung with a 10mm hole in it - would I get some suction across it?
 

two

Aug 4, 2011
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West Midlands
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A-Class Fiat
And it is also used as the ventilation pipe in Thetford's version of a SOG.
That's right. I think that the Thetford ventilation system is its sole purpose.
With SOG, the fan operates as soon as the flap is opened (a bit more practical).
 
Apr 22, 2018
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Adria Coral lowline
That is the Thetford version of a SOG. You know you have it if the first push of the flush button starts the fan which can be heard running.
Ohhhhhhh. Thanks for that info. I must have the version of SOG then as fan runs when button first pressed.

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Jul 5, 2013
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That's right. I think that the Thetford ventilation system is its sole purpose.
With SOG, the fan operates as soon as the flap is opened (a bit more practical).
Not really more practical. The fan on the Thetford starts on the first press of the flush button, which dors not release any water. That means you can start the fan before you open the flap, therefore ensuring you have a negative pressure in the cassette and no blow back. The secpnd press of the flush button releases the water.
 
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Stealaway
Jan 8, 2013
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Dronfield - Derbyshire
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I've come to the conclusion that the aroma(!) from the cassette only occurs when I drive with the windows open. It must be sucking up through the tube, into the cassette and out into the van
After reading about the possible consequences of blocking the vent I decided to retain the vent tube - funny though!

I've made this one way valve to fit the bottom of the vent tube as it exits the bottom of the van.

WP_20180429_12_14_48_Rich.jpg

Hopefully driving with the windows open will now cause the ball to be sucked up and block the vent.
I'll let you know the results next trip.

WP_20180429_12_15_01_Rich.jpg
 

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Dec 17, 2016
951
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Malvern
Funster No
46,488
MH
Hymer B525 2006 A cl
Exp
2012
Thanks to this thread I have realised that because I have a SOG fitted I don't have to worry about the pressure changes Lenny described. Great!

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Stealaway
Jan 8, 2013
8,478
11,516
Dronfield - Derbyshire
Funster No
24,202
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Burstner Lyseo 690G
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We've just got back from a week on the east coast and I can report my valve worked perfectly - no smells at all now from the cassette.
I also seem to have found the optimum amount of Bio washing liquid for my size cassette (100ml). We came back with it pretty full and there was still no odours from it at all - Non - Zilch - Nothing.

I'm never going back to blue chemicals.
 

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