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11-30-2019, 10:41 PM
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#1
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Senior Member
Join Date: Nov 2011
Location: Montgomery, Texas
Posts: 108
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Blacktank flush backfeeding/cross contamination?
I have a grand design 5th wheel with a black tank flush.
Previously I have always used a completely different hose for the black tank flush and a extremely careful about campground spigots to the point where I always use bleach before connecting.
During the walk through the dealer said on his unit he had made a Y with 2 separate shutoffs and only needed to turn on the correct branch of the Y to either fill the tank or flush the system and used only 1 hose.
Is this a good idea or is there a chance of cross contamination?
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12-01-2019, 07:02 AM
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#2
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Community Moderator
Monaco Owners Club
Join Date: Jul 2016
Location: Central, Arkansas
Posts: 11,294
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Dealer is an idiot you don't need your black flush hooked up until you dump. Keep doing what you have been doing, it's the right way.
There is check valve and chances are nothing would happen but it is so little effort to do it correctly it isn't worth the risk.
__________________
2004 Beaver Monterey Laguna IV
Cummins ISC 350HP Allison 3000 6 speed
2020 Chevy Equinox Premier 2.0t 9 speed AWD
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12-01-2019, 07:30 AM
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#3
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Senior Member
Join Date: Mar 2016
Location: SC
Posts: 364
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If you look at the design of the black tank flush, you will realize that more than one thing needs to fail in order to get black water backing out into the black tank flush port. I have always connected my black tank flush and city water line together when using my motorhome. In order to prevent the remotest of possibility of contamination I added a vacuum breaker/backflow preventer, https://www.lowes.com/pd/AMERICAN-VA...BoCrbkQAvD_BwE, after the Y connection to attach the black tank flush line to that so I have a redundant measure of protection.
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12-01-2019, 08:38 AM
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#4
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Senior Member
Outdoors RV Owners Club
Join Date: Oct 2014
Posts: 3,539
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Bacteria are microscopic and will not necessarily stop just because they encounter a vacuum breaker. Think about it. How much time are you saving? What are you willing to risk to save that amount of time?
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2020 F28 RKS Titanium
2017 Creekside 23 RBS Sold
2016 F250 Super Crew XLT Overworked
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12-01-2019, 08:44 AM
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#5
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Senior Member
Winnebago Owners Club
Join Date: Apr 2019
Location: fulltime
Posts: 680
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i use the y as well i am not worried. i use this order pressure regulator, to y one side filter to fresh water hose to inlet other side black hose to black tank flush inlet
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2006 winnebago adventurer 38t 2018 carry-on hawkline enclosed 8.5x20 2007 mini cooper convertible 2012 hd xl1200c
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12-01-2019, 08:54 AM
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#6
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Senior Member
Join Date: Nov 2015
Posts: 26,846
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City Water Inlet has a check valve so when using the on-board pump water doesn't backflow out inlet.
Black Tank Flush inlet does NOT have a check valve so any water in the line up to the anti-siphon device WILL flow back
Anti-siphon device is typically 2' above top of black tank
Black Tank would have to be filled ----so overfilled that contents go up vent line in order to force anything back thru spray nozzle/up and thru anti-siphon device and then back down and into hose.
Cross contaimination is Possible..........highly unlikely
Tank full enough will probably force contents out thru toilet
Anti-siphon will probably just leak inside sink cabinet
Water supply would have to be completely depressurized
Possible not not very probable
Personally I only connect flush hose when actually flushing tank
I would be MORE concerned with someone turning it on when I was not there or aware they did it........so why leave the hose connected when not actually flushing?
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I took my Medication today. HAVE YOU?
Dodge 3500 w/Tractor Motor
US NAVY---USS Decatur DDG-31
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12-01-2019, 09:16 AM
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#7
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Senior Member
Thor Owners Club Ford Super Duty Owner
Join Date: Jul 2011
Posts: 3,796
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Even with an air gap between the water source and the tank there will always be a potential for cross contamination. What each of us has to do is determine the risk, what our individual tolerances are and who to minimize the same.
Personally I would rather not have a permanent connection between the potable water and the contaminated waste side of the coach plumbing. Anything man made can and will fail and if installed on a RV will fail sooner than you might expect. Easy enough to connect a hose when the tank needs to be cleaned.
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2006 Hurricane 31D built on a 2006 Ford F53
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12-01-2019, 09:51 AM
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#8
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Senior Member
Join Date: Dec 2012
Location: Oregon
Posts: 6,657
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I use a Y when connecting to the city water spigot. Mainly because I use one of the new black flex hoses. Issue with the flex hose is they create a lot of back pressure and when trying to disconnect it takes forever for the water pressure to reduce enough to un-screw it. Water sprays for ever. With the Y I can use one side of it to relieve the pressure. I also hookup my black tank rinse hose to the other end but don't screw it into the black tank rinse on the trailer until I'm ready to rinse out the tank. I also use a back flow on that hose.
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12-01-2019, 11:01 AM
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#9
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Senior Member
Join Date: Sep 2012
Location: Palm Coast Florida
Posts: 12,995
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It makes sense to me, never use the fresh water hose on the black tank flush. I use a regular garden hose and never they other hose. Why would you ever take a chance of contamination. Especially when it is easy to avoid that risk.
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12-03-2019, 11:24 AM
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#10
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Senior Member
Join Date: Mar 2018
Posts: 1,643
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I dont see any advantage to using a Y.
If it saves you seconds of hose hookup are you really that tight for time?
__________________
Professional mechanic.
2018 Ram 2500 HD Mega cab.
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12-03-2019, 03:49 PM
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#11
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Senior Member
Join Date: Jun 2016
Location: Omaha, Ne
Posts: 427
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Blacktank flush backfeeding/cross contamination?
Quote:
Originally Posted by Old-Biscuit
City Water Inlet has a check valve so when using the on-board pump water doesn't backflow out inlet.
Black Tank Flush inlet does NOT have a check valve so any water in the line up to the anti-siphon device WILL flow back
Anti-siphon device is typically 2' above top of black tank
Black Tank would have to be filled ----so overfilled that contents go up vent line in order to force anything back thru spray nozzle/up and thru anti-siphon device and then back down and into hose.
Cross contaimination is Possible..........highly unlikely
Tank full enough will probably force contents out thru toilet
Anti-siphon will probably just leak inside sink cabinet
Water supply would have to be completely depressurized
Possible not not very probable
Personally I only connect flush hose when actually flushing tank
I would be MORE concerned with someone turning it on when I was not there or aware they did it........so why leave the hose connected when .............
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A lot of black tank flushes have a back flow preventers, my current wildcat 5th wheel has it and my previous camper 27hfs had it.
__________________
Curt
2015 Wildcat 295RSX
2014 Ram 3500 CCLB 6.7 cummins
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12-03-2019, 04:32 PM
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#12
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Senior Member
Join Date: May 2019
Posts: 1,211
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If you're so concerned with cross contamination that things like this actually make you worry, then you shouldn't be in an RV. There is absolutely no way to keep the systems totally separate without using new every time you connect something.
I pull in to a newly setup RV site and hook up my white potable water hose to the newly installed spigot and go on about my business. Eventually, I'll need flush my black tank, so I remove my new white potable water hose from the new spigot and attach my non-potable old fashioned rubber garden hose to the spigot and my black tank flush. Oh no! I just contaminated the new garden hose with poop bacteria! But that's okay, the water was only flowing one way so it didn't contaminate the spigot. When I'm done flushing, I put special black tank flush hose caps on the ends of the hose so that nothing leaks out. Now I put that hose back in storage and continue using the RV cuz that's where I live.
A few days or weeks go by, and that pesky black tank is full again. Time for another flush. I get out the capped off black tank hose and suddenly realize that the whole hose is contaminated with poop bacteria. It's been wet all this time and the bacteria have populated the whole hose! That's okay though, because it's just used for the black tank flush. I take off the white potable water hose off the new uncontaminated spigot once again and put the black tank hose on it, contaminating the spigot. Then I do my thing, and cap the hose once again to be sure that I don't cross contaminate anything. Then I take my white potable water hose that's never been contaminated, and hook it up to the freshly contaminated spigot. Run water through that hose and I've now contaminated my potable water hose and the entire fresh water system in my RV!
Sure, you can bleach the spigot, but even bleach isn't 100% effective. You're never going to kill all the bacteria. Would you lick the spigot at every campground you connect your water hose to? Why not? That's basically what you're doing every time you use the water there to cook or clean or just drink. You can even add fancy adapters and extra connections, but as long as you're using a single spigot for all your water needs, it's going to get contaminated. There is absolutely no way around it.
The best thing to do is simply stop worrying about it. The human immune system is set up to handle all that stuff. It's truly a wonderful thing, but it needs to be taught how to do its job. That's why babies put everything in their mouths. They are teaching their immune system about which bacteria are normal and not a problem, as well as which ones are a problem. If they never experience normal bacteria as a baby, their body doesn't learn that it's okay, so when they experience it later in life, they have allergic reactions and can't handle it. People need to be exposed to some bugs. It's healthy for us. Raising babies in sterile environments does them far more harm than good. Sure, they might get sick fewer times in infancy, but they'll have a much worse time in adulthood.
Don't misunderstand! I'm not saying you should be as dirty and nasty as possible. I'm just saying that you shouldn't worry so much about being perfectly sterile either. That cookie that fell on the floor is fine even if you've walked on that floor with your shoes on. The 5 second rule has its merit. I wouldn't eat spaghetti that fell on the floor, but a cookie or a grape from the floor once in a while is okay.
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2014 F350 DRW 6.7L CC FX4 King Ranch Ruby Red Metallic 158,000 Miles 4,450 Hours
2018 Cherokee Grey Wolf 29TE | Because I'm home, no matter where I am.
2018 Honda CB650F | Because the truck leans the wrong way when I turn.
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12-04-2019, 11:11 PM
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#13
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Senior Member
Join Date: Jan 2013
Location: 7S5
Posts: 658
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We travel with three dogs. The dogs like to sit on our couches and laps. Sometimes I let them eat dog cookies out of my bare hands. Sometimes dogs eat things we don't think they should... I grew up with dogs (and cats too) and somehow we have survived all that cross contamination. I have been "camping" much of my 76 years. I also use a "Y" fitting on the fresh water bib, I only hook the flush to it when it's time to flush tanks. I shut off the fresh water at the "Y" and I drain the black tank first, close the black valve and drain the grey, close the grey valve and then flush and dump. When finished I disconnect the flush hose after flushing it out. So far we are still alive and healthy. I think common sense has kept us that way.
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2004.5 GMC SLT CCLB, Ride Rites, Turbo brake, EFI Live
2012 Arctic Fox 29 5T 5th Airborne, B&W, Prodigy
Papillon navigators Lily, Buddy and Willow
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12-08-2019, 09:47 PM
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#14
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Senior Member
Join Date: Nov 2011
Location: Montgomery, Texas
Posts: 108
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Thanks for all the insight it seems to be fairly balanced on the way to do things so I think I will stick with the way I have always done things and ignore the dealer
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