Cheap Water Manifold Addition for flushing tanks

[jkxtreme]

Even though our 5th wheel is a 2023, we got it used. It sat for a number of months with 'stuff' in the two black tanks which caused us some issues. We had a company called Kleen Tank pressure wash the inside of the tanks to get the clean and afterward they made some good recommendations. One of those recommendations was to flush each black tank with 8-10 gallons of water each time after dumping, then add 5 gallons of water to the tank. Instead of swapping hose connection each time we do this, we installed a manifold with integral ball valves that allows us to flush without disconnecting anything.
I created a video describing what we did. The link is below. Less than $200 and it works well.
https://youtu.be/JCaFXPbtY7c

[Todd & Mary]

Those check valves are NOT certified nor adequate for Black tank service! Do yourself a favor and invest in check valves certified for that use. Otherwise, you could have a disaster on your hands. Personally, I would never combine fresh and flush hoses together.

[jkxtreme]

Thanks for the heads up. The ball valves in the manifold and elbows should only ever see fresh water. The check valves are built into the rv.
I will watch to make sure that doesn't happen but your insight is appreciated so I will be wary.

[BB_TX]

Impressive setup. I followed a far less scientific method. A dual shutoff Y valve at the park faucet, one hose to fresh water and one hose to black tank flush. When draining the black tank I would drain the tank, when drained close the valve, open the water to the flush input for 1 - 1 1/2 minutes, open tank drain valve with flush still running and watch for solids passing thru my clear sewer extension, close the drain valve for another 1 - 1 1/2 minutes, open drain valve and watch for solids, maybe repeat again if any significant solids seen, close drain valve for another minute or so to get some water in the black tank. Worked fine for 14 years with no issues. Cost? What ever that Y valve cost; $5 maybe???.

[jkxtreme]

Excellent idea. I tend to over think projects. Maybe I need to take a more simplistic approach.

[BB_TX]

Even though I am an engineer by trade (retired), I tend to move toward the more simplistic methods. During my working life I saw a lot of good engineers who over analyzed issues to the point of being under productive.

[DutchmenSport]

Why not just hook up a 3rd valve, like a Flush King on your tank outlet and simply back flush the grey water tank into the black water tank and flush out the black tank. It takes NO more water and flushes out the black tank very well. If the grey tank is full, you can back flush 3 or maybe even 4 times. The last back flush, simply close off the black tank and leave the water instead of adding even more water. Then use the remaining bit of grey water to flush out the sewer hose.

Back flushing does not use any additional water, you can do it even if you have no additional water source, and you are recycling your grey water for another purpose, a useful purpose.

If you back flush every time you dump the black tank, the black tank does not get any build-up in it. I have a black tank flusher, and very, very seldom ever use it because the back flush works so well.

Water conversation is one of those areas of responsibility that we all need to consider as avid RVers.

[jkxtreme]

Great suggestion. We were using the grey water to back flush the black tanks but we couldn't get the caked material from the black tanks. We were also concerned about cross contamination, but that might not matter.
We'll use the manifold arrangement when we're connected to water, and use the grey water flush when we are not connected.
Thanks for the response.

[Todd & Mary]

Originally Posted by jkxtreme

Thanks for the heads up. The ball valves in the manifold and elbows should only ever see fresh water. The check valves are built into the rv.
I will watch to make sure that doesn't happen but your insight is appreciated so I will be wary.

Thats what I was told also. When I disconnect the flush hose from the RV flush. There is water flowing back from the tank flush ports. Which is a no go! for health safety.

[BB_TX]

Originally Posted by Todd & Mary

Thats what I was told also. When I disconnect the flush hose from the RV flush. There is water flowing back from the tank flush ports. Which is a no go! for health safety.

If you have not modified your flush system, that water is just clean water in the first half of the flush system. And can’t flow back as long as connected to a pressurized water system. In the middle the pipes rise a couple of feet or so. At the highest point there is an antisiphon valve that prevents any water being siphoned back to the water connection port. The water in the last part of the system drains into the black tank. And all of that is clean water.

[RMcNeal]

A simple solution is to put a $5 backflow preventer on the hose connection for the black tank flush. It's extremely unlikely to backflow into the fresh water anyway, but for $5, it's cheap insurance.