I installed a twist-on knife valve

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Joezeppy

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Mar 16, 2009
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Location
Upstate NY - Kuyahoora Valley
A few members have talked about them and it seemed like the perfect solution to stopping the half ounce of stuff that would drip out every time I removed the sewer cap. It's about a 3' run from my black tank valve to the cap which I think is the issue (rather than an actual leaking valve).


I experimented a bit at the dump station this weekend after 4 days with electric only.
  • Emptied the black as usual and left the black valve open
  • Closed the twist-on
  • Opened the gray for maybe 15 seconds which allowed water to backup into the black tank
  • Closed the gray
  • Opened the twist-on
  • Did this maybe 3 times and it appeared most of the solids had been emptied
  • After closing the black and opening the gray again, I also closed the twist-on a couple of times to fill and clear the 3' of black waste pipe

To paraphrase Jeff Foxworthy, "You might be a true RVer if you get excited about emptying your waste tanks!"  ;D
 
Of the valve? Or me operating it?  ;D


Yes, its' this one: https://www.amazon.com/gp/product/B000BGHYJS?pf_rd_p=d1f45e03-8b73-4c9a-9beb-4819111bef9a&pf_rd_r=Y9WVHBWXRXQVAAP3WTF0

 
I got the same one, and seeing some other reports, I have the same issue.  It works great, just like it's supposed to.  But be very careful when disconnecting your slinky hose.  It has a tendency to want to pull the entire unit off.  I had my first real outing with it this past weekend and learned this.  No big mess, but a little heartstopper there for a minute.
 
Just drill a small hole through the side of the connection surface and install a stainless steel sheet metal screw.
 
Rene T said:
Just drill a small hole through the side of the connection surface and install a stainless steel sheet metal screw.

That was exactly my thinking.  Now all I have to do is get myself a roundtuit!!!
 
I also use one sometimes.  I have a kitchen grey tank that requires me to close our slide to hook up the hose for dumping.  If we're going to be hooked up for an extended period of time, I put the valve on the end of a sewer hose hooked to the kitchen dump valve.  I can leave the kitchen tank valve open all the time and hold the liquid with this valve.  I like to allow my kitchen tank to be almost full before I dump just to make sure it flushes out quickly so any residue will flow out.
 
Have a small box of round Tuits in the basement.  If you will PM your address...

I also have a knife valve on the end of my sewer line.  The gray tank will not close completely, so there is always water behind it!  It does keep the cap dry, though!  I like having it there.
 
edjunior said:
But be very careful when disconnecting your slinky hose.  It has a tendency to want to pull the entire unit off.  I had my first real outing with it this past weekend and learned this.  No big mess, but a little heartstopper there for a minute.
Yup. After trying one hand to hold it and one to unscrew the hose I propped my knee against it to stop it from turning. I like the screw idea.
 
You're welcome, Ed. I couldn't get a picture of the screw on the back of the twist-on valve, but I knew the photo of the screw on the 45 deg elbow on the front would get the idea across anyway.
 
Make sure you use a screw just long enough to hold it in place. Using a screw that sticks out into the flow with snag solids.
 
kdbgoat said:
Make sure you use a screw just long enough to hold it in place. Using a screw that sticks out into the flow with snag solids.

The self-drilling screws I used stick out about 3/8". I've never seen anything stuck to the one I can see through the clear elbow.
 
Yep. My post was more for other folks who do this without thinking it through.
 
I've put the valve on our last 3, 5th wheels to eliminate the surprise that sometimes is there. I have always been happy with the added security it gives.
 
It's funny...I never had this issue with my old TT.  But with the 5th wheel, it started early and just got worse.  It's not real bad, but it does make me wonder what the heck is going on with the newer units.  My TT was a 2005.
 
I don't have any issues with the valve twisting but I do like having a backup to keep any fluid from leaking out of the cap.
 
Joezeppy said:
A few members have talked about them and it seemed like the perfect solution to stopping the half ounce of stuff that would drip out every time I removed the sewer cap.

A half ounce is nothing. 

I forgot to close the black and gray valves on one of my camping trips, but did have the sewer cap on the end of the drain line.  An interesting story and it happened while waiting in a dump line (i.e. an audience) to drain my sewer tanks...

And I am a bit smarter now.
 
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