Gray Tank Flush & Why You May Need it...

[Wyatt]

Many people have noticed that their gray tank smells as bad or worse than their black tank. Mine never did, but while installing this gray tank flush, which is nothing more than an aftermarket black tank flush that I also just installed, after cutting a hole in the side for the Tornado flush, I stuck my finger into the hole and found a thick (probably 1/16”) coating of sludge on the inside of the gray tank. Now, the black tank inside was clean when I installed it there, so I was shocked to see the accumulation of sludge on the gray tank.

We always thoroughly wipe our dishes clean before washing them and never put grease down the sink. Most of what goes down there is soapy dishwater or water from the shower.

Turns out that flushing the gray tank is equally important to help keep your sensors reading properly. My blank tank (Miracle Probe) sensors I’ve never had an issue with, but the gray tank ones I did, and now I know why…

Here's a link to the video showing the fix and the issue...

[Eagle5]

I add a ½ cup of Borax down into the Grey Tank as I start a trip; spread-out between my sinks and shower drain. I know it really keeps my traps looking clean.
Eagle5

[Wyatt]

Originally Posted by Eagle5

I add a ½ cup of Borax down into the Grey Tank as I start a trip; spread-out between my sinks and shower drain. I know it really keeps my traps looking clean.
Eagle5

Traps or tanks? We use the same treatment in our black tank as our gray tank. Yet when I installed these two backflush devices, and I cut the hole, I was able to see inside. The black tank was like new inside and the gray one covered with a black slime on the side walls.

What’s the difference? I always back flushed the black tank and even put the wand down the toilet.

I never thought the gray tank would need flushing, right? I mean everyone uses that water to flush out their hose at the end.

I was wrong. It too needs a good backflush…

[creativepart]

I clean my gray tank about 3-times a year. I haven't installed a tank flush, but I use an external device that feeds water back into the gray tank under pressure. It works pretty well.
https://www.amazon.com/Valterra-Degr.../dp/B008O9DV78

https://www.youtube.com/watch?v=oi8HUknP46Y

[Ray,IN]

I agree, it's amazing how much body/skin oils and cells we wash off every day. I add automatic dishwasher liquid soap once a year in my waste tanks.

[Scotty B]

Thx for the tip on that back flusher Paul. Gonna give that and the water meter a try.
I have two grey and two black tanks, total capacity of 85 and 80 gallons respectively, but can't find the individual tank capacities. Any idea on that info? Assume the black might both be 40, but the grey?
Thanks as always and safe travels...
Took the rig, Bronco, and Ben on their first boat trip!

[creativepart]

Originally Posted by Scotty B

I have two grey and two black tanks, total capacity of 85 and 80 gallons respectively, but can't find the individual tank capacities. Any idea on that info?

Hey Scott,
Those tank sizes or on the Specifications page for the 36Z on the Winnebago website:

Holding Tank Capacity — Black (gal.) 43 & 32
Holding Tank Capacity — Gray (gal.) 44 & 39

Now… which tank has which capacity???

[Scotty B]

Thx Paul...determined with aid of the water meter that the smaller tanks are the front ones. Had to be creative with the set up, but the flusher worked OK. Basically what I found is that our tanks are in really good shape - hardly anything came out even after three or four flushes. Wipe our dishes, use plenty of water, and use the blue juice in all tanks. Also, have clean water and juice in the tanks before travel. Finally, I believe the water softener makes a big difference.
Safe travels!

[Scotty B]

Pics...

[Wyatt]

You know, I posted this because I was so surprised at what I saw inside the gray tank when I cut that hole. The sides of the tank had a black slim on them.

The reason I posted this video was because, although I treat my gray tank with the same chemicals as the black tank, and I also back flush both tanks with the one showed above, and I use a water meter like that one too, and the WATER RUNS OUT PERFECTLY CLEAR, only the gray tank had this slim on the inside walls.
The ONLY difference is I would also flush the black tank with a wand down the toilet.

Conclusion: There’s probably a lot more build up of stuff in your gray tanks than one would imagine…

[Scotty B]

Thx Drew...just watched the video...really nice job. I am sure my grey tanks and sensors are just like your's were. Interestingly, I just have a sensor issue in the front grey tank which drains the galley, washer/dryer, and half bath. The rear full bath sink and shower is fine. We used fabric softener at first and that's when we started having sensor issues. Goes down to three, but no further.
Going into the shop and storage for a month while we visit family. Maybe leave them empty and see if they dry out and flake? I can't see installing a tank flusher on it for now.
Safe travels!

[marudnick]

Originally Posted by creativepart

I clean my gray tank about 3-times a year. I haven't installed a tank flush, but I use an external device that feeds water back into the gray tank under pressure. It works pretty well.

When we purchased our RV, I believe that I purchased an external tank flush. When we did our PDI, the tech said we should return it because it wouldn’t do any good, because there are bends in the plumbing (see below). He suggested a wand, which we use for the black tank a couple times a year. (https://www.amazon.com/Camco-Straigh...000BUQOCC?th=1) That helps but it’s a bit of a hassle and it doesn’t get the grey tank.

Will the flush you use work for my rig?

[Marine359]

Twice a year, before leaving on a trip, using a bucket, we put 1/4 cup of bleach, 1/8 cup Dawn dish soap, and 5 gal of water lightly stirred into the gray tank through the galley sink. The solution gives the gray tank a thorough scrubbing. We empty and when we reach a dump station, and flush by opening all taps for a few minutes. Then empty agian to wash out any residual bleach. Never had a smelly gray tank by this simple protocol.