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'That smell'

We're getting it when the roof air is on. What do you all add to the BW tank when it happens?
1993 U-240 "La Villa Grande"..CAT 3116 w/ Pacbrake PRXB...Allison 3060 6-speed..
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                                      Build # 4297
                                      PNW natives
                      Home base:  'Cactus Hug' (Ajo, Arizona)
                        DW Judy & Chet the wonder dog
                        Full-Timers 'Sailing the asphalt sea'

Re: 'That smell'

Reply #1
Dawn helps and also products with oxiclean  works well also.
1995 U320 40', 2013 chevy sonic toad, my real love are corvettes have owned 30

Re: 'That smell'

Reply #2
If your coach is closed up. No windows or doors open and you have the kitchen exhaust fan on it will pull fumes up from the black water tank through the toilet. You must have an outside source of make up air when that large fan is running.
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Gerry & Brenda
CHARLOTTE HARBOR, FL
1994 Grand Villa - # 4466
U300 Unihome - 6V92 Detroit
4 speed Allison - Jake Brake

Re: 'That smell'

Reply #3
We use Dawn (1/2 cup) and Calgon (1 cup) dissolved in a bucket of hot water, then poured down the drain.  Works for both tanks.

Make sure the toilet, and the sink and shower drain water traps, are kept full of water.

Check your rooftop holding tank vent to be sure it is clear.  Birds have been known to nest there.

Check the air admittance valves to be sure they are functioning correctly.  Usually one in the bathroom behind the toilet, one under the kitchen sink, and possibly one under the bathroom sink.  Search "air admittance valve" on the Forum, or start with this thread for more info:

Odor Problem
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
"It goes without saying..."


Re: 'That smell'

Reply #5
Mike,
  As mentioned above it is likely a failing air admittance valve. Good time to replace all of them. If you do I recommend you buy Studor valves. They are pricey but will not let you down. For now you can just keep positive pressure in the coach and keep that odor where it belongs.
jor


Re: 'That smell'

Reply #6
Yup, the right answer is NOT to try to make the gray or black tank smell good, but to find the source of the odor.

Locate the SOURCE.  If under the sink in kitchen or bathroom, the air admittance valve(s) are the likely source.  This is assuming the smell is that of the tank(s).

If the smell is a "wet dog" odor when you turn on the roof A/C, that is a completely different issue.  The roof A/C EVAPORATORS need to be cleaned.  Done from the roof, and not that difficult on your brand of A/C.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: 'That smell'

Reply #7
Yup, the right answer is NOT to try to make the gray or black tank smell good, but to find the source of the odor.

Locate the SOURCE.  If under the sink in kitchen or bathroom, the air admittance valve(s) are the likely source.  This is assuming the smell is that of the tank(s).

If the smell is a "wet dog" odor when you turn on the roof A/C, that is a completely different issue.  The roof A/C EVAPORATORS need to be cleaned.  Done from the roof, and not that difficult on your brand of A/C.

It is not recommended that one use bleach to clean the mold that can grow on a too wet Evap coil. Go get a can of AC mold killer. One can also put the AC in fan only mode to dry out the EVAP before shutting it down. Putting it away wet is what causes the wet dog to come home. My Mercedes had this issue in a bad way.

As for the outhouse stench. I replaced all my AAV's and I was still getting ill winds from the black tank. What helped me was learning about those two little over flow holes high up in the bowl.  Those have P traps just like your sinks. I just take a small water bottle that's going in the trash and pour some water in each hole. I also ditched the over priced deodorizing RV tank stuff and got some RidX septic tank stuff. Because our black tank is a septic tank. That has really helped. And it's less costly per dose as one only needs about .5 ounces.
Jerry & Nona and Kimeru the cat that thinks she's a dog
1998 36' WTFE U320  #5314 Motorcade #17711
USAF 1975-1995
2019 Subaru Crosstrek 'toad'
2003 Subaru Legacy touring car
jerry Fincher | Flickr

Re: 'That smell'

Reply #8
Mike,
  As mentioned above it is likely a failing air admittance valve. Good time to replace all of them. If you do I recommend you buy Studor valves. They are pricey but will not let you down. For now you can just keep positive pressure in the coach and keep that odor where it belongs.
jor




Jor, the ones that sell for $5 or $6 at HD or Lowe's work just as well and are right there with the high dollar ones!  Just an FYI.
Joe & Dottie Allen
Sold!  December 2023.      2000 U320; build # 5645
Our coach " Maxine"
Motorcade #  15922;  Escapee 150950; FMCA F330833; Boondockers Welcome;  Harvest Hosts;  Thousand Trails
'98 U320 from 2000-'06
USAF '62-'66

"Do not spoil what you have by desiring what you have not; remember that what you now have was once among the things you only hoped for." ―Epicurus

Re: 'That smell'

Reply #9
Quote
the ones that sell for $5 or $6 at HD or Lowe's work just as well

One would think so but that has not been the case for me. On two rigs I have replaced the valves with the Home Depot off the shelf ones and two (one on each coach) did not do the job. I know. Doesn't make sense to me either. I do know, however, once I installed the Sudors I never had another issue.
jor

Re: 'That smell'

Reply #10
Qaulity products are always a bit more $ knock off don't care much, and China doesn't care in the very least, China just says try to sue me!
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: 'That smell'

Reply #11
Brett's idea that the odor might be coming from the air conditioner is probably correct, There is no air intrusion from the roof, the units recirculate the inside air and don't pull outside air. If the problem is only when running the air that might be the issue.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: 'That smell'

Reply #12
Well yes and no, the roof a/c most likely has an axle shaft that penetrates the suction side of the evaporator supply fan housing thru an unsealed oversized hole downstream of the high static pressure drop filters and evap coil so any odors drifting across the roof will get sucked into and  mixed with the supply air, along with some 130+ condenser coil air. Crappy design cubed.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: 'That smell'

Reply #13
I had nasty smells coming from the vent holes in the toilet bowl  I plugged them and life got less smelly.
1998 U270 34'

Re: 'That smell'

Reply #14
The holes in your toilet bowl are overflow holes. I got plugs (free) from the Mfr.
Seems overflow isn't necessary when a user has to hold down (or up) the control to add water.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: 'That smell'

Reply #15
We use Dawn (1/2 cup) and Calgon (1 cup) dissolved in a bucket of hot water, then poured down the drain.  Works for both tanks.

Make sure the toilet, and the sink and shower drain water traps, are kept full of water.

Check your rooftop holding tank vent to be sure it is clear.  Birds have been known to nest there.

Check the air admittance valves to be sure they are functioning correctly.  Usually one in the bathroom behind the toilet, one under the kitchen sink, and possibly one under the bathroom sink.  Search "air admittance valve" on the Forum, or start with this thread for more info:

Odor Problem

What Calgon product are you using?
1995 U320C SE 40'
Jeep 4x4 Commander - Limited - Hemi
"The Pack"  Yogi and Diesel our Airedales -  Charlie our Boxer/Akita mix. Gone but NEVER forgotten Jake our yellow Lab.
NRA Law Enforcement Firearms instructor - Handgun/shotgun
Regional Firearms instructor for national Armored Transp. Co.

Re: 'That smell'

Reply #16
Well yes and no, the roof a/c most likely has an axle shaft that penetrates the suction side of the evaporator supply fan housing thru an unsealed oversized hole downstream of the high static pressure drop filters and evap coil so any odors drifting across the roof will get sucked into and  mixed with the supply air, along with some 130+ condenser coil air. Crappy design cubed.
I don't know the works of all the roof air units, but the ones I have worked on have a plastic cover with a gasket sealing from all outside air covering the squirrel cage for the supply and return.



1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: 'That smell'

Reply #17
Calgon Ocean Breeze Moisturizing Bath Beads.

Calgon Ocean Breeze Moisturizing Bath Beads with Aloe & Vitamin E, 30 oz -...
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
"It goes without saying..."