black water drain line

It's a common problem. The hanger is a cheap piece of strapping that is not well suited to withstand the constant banging up and down of towing. Many times it will snap off, other times, the screw and nut will vibrate loose. I've seen some merely add a good heavy duty wire tie to help support the pipe. I've also seen some put a big hose clamp or u bolt connector and attach a more solid hanger. The 172 is exempt from this problem (luckily for me) and I believe one other model too, because we have a single drain pipe for black and grey, and there is much more support given by the 2 combined drain pipes than the stand alone pipe. You would think these silly little problems that would cost about a dollar more to fix at manufacture, with a thicker hanger and self lock nut,  would be done by the year 2018, but.........

I have two videos on the topic, the first is what I went through coming back from FL last March and the second is the strapping I used to secure. Lots of miles since with no issues. ~PP

Both my 3 inch black tank line and 1 1/2 inch gray line have broken loose. Stress was the problem on the 3 inch line but corrosion got the gray line. The FR straps are apparently just mild steel, I replaced with stainless hose clamps and hardware. As you have to inevitably go to the trouble of reengineering these supports for FR anyway, might as well use proper corrosion resistant materials. Just sayin'. 

Originally posted by thcopa How to replace the plastic t-handle on the black line

Empty tank first. Valve is bolted on with 4 bolts. Remove, pull valve off and put new valve on and re-bolt.

I have to replace mine too....it leaks about a cup of "gravy" inside the cap every time.