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Air Admittance Valves

I have a general question about air admittance valves versus through the roof sewer vents.  Do air admittance valves exactly perform the same function as through the roof vents?  In other words, if I install these valves at all the critical places, could I completely eliminate all through the roof vents? 

Thanks,

Richard
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Air Admittance Valves

Reply #1 –
Richard,
Air Admittance Valves (AAV) are one-way vents installed after the trap on the drain line of a fixture. They're designed to address negative air pressure in the drain system, created when a fixture is drained.

a traditional, passive, external venting system will always be superior (especially when it comes to positive pressure)




Frank & Daisy
NO LONGER  "looking for the perfect Foretravel
36' or less non slide preferred."  She has been found and is ours.
2003 U320 36' non slide  Unit 6103
Cummins ISM 450
Allison 4000MH

Re: Air Admittance Valves

Reply #2 –
Quote from: Jan & Richard –
...could I completely eliminate all through the roof vents? 
No.  Consider the total system.  A properly designed roof vent will create a constant slightly negative pressure in the holding tank.  Air admittance valves admit fresh air to the tank in response to negative pressure.  Same when you flush the toilet.  Interior air goes down the toilet - odors go out the (2-way flow) roof vent.  We turn OFF the bathroom vent fan when flushing to avoid "reversing the direction of black tank air flow".

Photos below:  1.  Foretravel OEM Vac-U-Jet venturi vent  2.  Camco Cyclone vent  3.  Lippert "360" Siphon vent


1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Air Admittance Valves

Reply #3 –
Thanks guys.  These two posts answer my question. 

Richard
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Air Admittance Valves

Reply #4 –
Cyclone vent or lippert vent. Which is the best and the most used?
Peter
Peter    Alberta Canada
'98 U320 40'  Build 5359 M11 450 HP, Aqua hot, Blu Ox

Re: Air Admittance Valves

Reply #5 –
I think the 360 works well for me. Always have a negative pressure on the tank IE no smells and no moving parts

Re: Air Admittance Valves

Reply #6 –
I replaced the OEM (venturi) vent with a Cyclone 6 years ago.  Other than turning yellow from UV exposure, it has held up well.  It still rotates freely in the slightest breeze, and keeps our holding tanks odor-free.

NOTE:  Our (GV) roof is flat, hence the Cyclone vent is mounted in a fairly vertical position.  On a curved (Unicoach) roof, the Cyclone may not rotate as freely due to being mounted in a slightly tilted position.  The Lippert 360 might be a better choice?  I don't know - I've never tried one.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Air Admittance Valves

Reply #7 –
I like the Cyclone vents.  If I hear them rattle in the night, I know to put the awnings away before the wind gets 'em.
Matt B
1998 u-320
 

Re: Air Admittance Valves

Reply #8 –
This has been my experience now on several different rvs.  I definitely prefer the Lippert 360.

What is broken on the roof?
97 U295 40, Build #5040, 6C8.3 325 HP
Oregon Continuous Traveler
Samsung Residential #RF20HFENBSR,
Xantrex SW2012, (3)AGM8D Hse, (2)AGM Grp24 Eng, Victron BMV-712, 1800w Solar 4 LG & 2 Sunpower
Extreme Full Body Pt w/hdlmps, new furn/floor, 4 down Lexus 2004 GX470 AWD curb weight 4,740 lbs
Prev: 1990 Barth, 10L 300 2 yrs; 91&92 Monaco Signature, 10 yrs, 10L C 300 &  6C8.3 300; 1997 ForeT 6C8.3 325 since May 2017.  Employed by Guaranty RV 14+ yrs.  Former VW New Car Dlr/Service Dlr, Sales Mgr, Rv Sales, and Service Adviser from 1968-2017
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