Blank Tank Flush

[2825Matheny]

I'm new to RVing and picking up a GD 303RLS next week. I have been reading and searching this site for a couple of years and have learned a lot. I was at the dealer today and had lot's of questions. One thing were were talking about was water hoses for city water and for the black tank flush. I have seen on here where 2 different hose are recommended to prevent contamination of the city water hose. The dealer said this was not necessary as the black tank connection had a built in backflow preventer and I could just move the city water hose to the black tank flush. Is this correct. If not do I use 2 hoses with a Y connector with shutoffs at the campground spigot. What's the best way to set this up? Thanks!

Tell me you did not write this post just to make my head explode!
Here are the facts (let's stay clear of opinions):
You do not need two hoses.
There is not a back-flow device in the black tank nozzle supply piping. There is a vacuum breaker up behind the shower. That's not the same as a back-flow device.
Never, ever, permanently connect a water line to the black tank and leave it hooked up. Got it?
Hook up to the black tank nozzle and run it for as long as you see fit to rinse the black tank. Then disconnect the water hose. When you do that, water will empty out of the black tank nozzle piping on to the ground. This is normal and expected.
Keeping a hose hooked up all the time keeps that pipe full of water. It never drains. Now, think about the bacteria in the black tank and their ability to swim. If the piping is full they are going to swim. If the pipe is empty then they don't swim far.
What I have done is put short hoses with male quick connect fittings on both my potable water supply and the black tank nozzle supply and a female quick connect fitting on my supply hose.
This way it is simple to disconnect and reconnect as needed.
I worked as a Manufacturing Engineer in the food industry before I retired. A very large part of what I did was sanitary piping specifications and design. I've worked with some of the best Sanitation Engineers and Mechanical Piping Engineers in the world. Trust me on this, do NOT listen to anyone that says hooking up a potable water supply to a pipe that goes to a septic tank any differently than what I have described and says it's a good idea.

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[Cate&Rob]

With no offense to anyone and great deference to others who have done this longer...

Why would anyone not spend an extra few bucks for a separate black water hose just for the peace of mind? Worse comes to worst, it's a backup for your primary.

Hi Jeff,

Because the "peace of mind" in having separate hoses is a false security. Two hoses connected at the same time is the "red flag". With a single hose, you can never make the mistake of having hoses connected to the potable water and the black tank flush at the same time. It is disturbing how often you see this in any campground .

If you choose to (or have to) use the water connection at a dump station, having a dedicated hose for this as suggested by @camper1013 does make a lot of sense.

Rob

[JColeman]

Hi Jeff,

Because the "peace of mind" in having separate hoses is a false security. Two hoses connected at the same time is the "red flag". With a single hose, you can never make the mistake of having hoses connected to the potable water and the black tank flush at the same time. It is disturbing how often you see this in any campground .

If you choose to (or have to) use the water connection at a dump station, having a dedicated hose for this as suggested by @camper1013 does make a lot of sense.

Rob

Hi Rob,

Thanks, yes. I completely understand the problem with a T water connection. I guess I don't resent the extra work of using a second hose to flush black tanks and a little sanitizer before hooking the fresh water back up. And since I know many don't sanitize, I also do a little bit of sanitizer before hooking up fresh water the first time as well.

OTOH, if I drop our steaks in the fire, I have no problem brushing them off (no sanitizer) and eating them.

[Jims94vmx]

One thing not mentioned, don't leave your black hose hooked up. Unhook when you are done. That leaves no chance of it overfilling.

[bertschb]

Since we're on the subject of black tank flushing I thought I'd mention a new "expandable" hose I started using this winter for the black tank. I was a little skeptical of this expanding thing but it's actually pretty cool. It shrinks to 1/3 it's length when unpressurized and has a shut off valve at the end. The shut off valve is very handy because I can turn the water on and off while flushing the black tanks without walking back and forth to the water pedestal.

Here is the hose I got:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I can't speak to their longevity because I've only used it a couple months but I'm happy with it so far.

[CoChris]

I have a second hose for the flush. I'm not so much worried about the black tank backing up as the contamination from the dump station area. When your at the dump station watch what others do with the hose once. You'll never want your fresh hose anywhere near it. Not to mention if you accidentally drop the end of the hose in the danger zone around there.

I am in the two hose camp. Many times I have found the water supplied at the dump stations is clearly posted as "Non-potable". I do not want to run any non-potable water through my drinking water hose.

Chris