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CnJ4TMs · 08-16-2022, 04:47 PM

I have a 2003 2720SD that developed leaks along the longest inverted rib of the graywater tank. I found numerous cracks at the bottom of the longest V-channel that spans the 30 gal tank. The length of this section of cracked v-channel was about 16 inches. I speculate that numerous cycles of the tank bottom bulging under the weight of 25+ gallons of graywater would have the effect of spreading apart the walls of the "V", and over time causing stress cracks. I wanted to repair in place to avoid a lot of headaches.

Anyway, I found a youtube video from 2015 that showed good directions for RV tank repair. To find it, Google "trailerdayz repair youtube" and select the Aug 6, 2015 25:01 video. Note: I had used these directions twice before for repair to a hairline crack and to a thumb-sized hole (!) in the black ABS pipe on my TM back in July 2016. No leaks from those 2 repairs over 6 years ago!

I followed the video directions using homemade thick slurry from black AB pipe shavings plus black Medium ABS cement. (Drilling into ABS pipe works good to get the shavings--clamp the pipe securely and beware a sudden torque to drill when bit breaks through the pipe!) I laid down 2 patch layers with black fiberglass window screen material in each layer for more strength. I then continued adding more patch layers to fill up the inverted v channel and finished with 2 plain coats of ABS cement.

I filled up the entire length (about 40 inches) of that main v-channel rib. It is tedious work on your back in close quarters under the TM. Because you are applying thick layers to fill this channel, you want to give each patch layer plenty of dry time (a week or more) to get good and hard. I used a wood plane to shave down high spots near the end of the process, before finishing off with 2 layers of ABS cement. All told, I took about 5-6 weeks to finish it.
I am retired, 68 yrs old, in no hurry, lol!

To reduce future stress to the repair, i installed a 36 inch long, right-angle thick sheetmetal brace, running front to back (parallel to the TM length) under the center of the tank. I had to custom -make 2 very stiff metal braces that i attached to each side of the long brace, then bolt these to the even-thicker frame material above and near each end of the tank.

The repair withstood a 30 gallon fill to capacity, no leaks. I could see the 36-inch brace bowing under the pressure of that much water on the bottom of the tank, then it returned to straight after dumping the water. An I beam type brace would provide more support.

Traveling far with a nearly full tank, after boondocking and enroute to a dumpsite, may have been the straw that broke the camel's back, causing the cracks to advance toward leak stage. So for prevention, I will try to dump
ASAP in future trips!

Charlie

08-16-2022, 04:47 PM	#14
CnJ4TMs New Member Join Date: Mar 2016 Posts: 3	Graywater tank leak repair I have a 2003 2720SD that developed leaks along the longest inverted rib of the graywater tank. I found numerous cracks at the bottom of the longest V-channel that spans the 30 gal tank. The length of this section of cracked v-channel was about 16 inches. I speculate that numerous cycles of the tank bottom bulging under the weight of 25+ gallons of graywater would have the effect of spreading apart the walls of the "V", and over time causing stress cracks. I wanted to repair in place to avoid a lot of headaches. Anyway, I found a youtube video from 2015 that showed good directions for RV tank repair. To find it, Google "trailerdayz repair youtube" and select the Aug 6, 2015 25:01 video. Note: I had used these directions twice before for repair to a hairline crack and to a thumb-sized hole (!) in the black ABS pipe on my TM back in July 2016. No leaks from those 2 repairs over 6 years ago! I followed the video directions using homemade thick slurry from black AB pipe shavings plus black Medium ABS cement. (Drilling into ABS pipe works good to get the shavings--clamp the pipe securely and beware a sudden torque to drill when bit breaks through the pipe!) I laid down 2 patch layers with black fiberglass window screen material in each layer for more strength. I then continued adding more patch layers to fill up the inverted v channel and finished with 2 plain coats of ABS cement. I filled up the entire length (about 40 inches) of that main v-channel rib. It is tedious work on your back in close quarters under the TM. Because you are applying thick layers to fill this channel, you want to give each patch layer plenty of dry time (a week or more) to get good and hard. I used a wood plane to shave down high spots near the end of the process, before finishing off with 2 layers of ABS cement. All told, I took about 5-6 weeks to finish it. I am retired, 68 yrs old, in no hurry, lol! To reduce future stress to the repair, i installed a 36 inch long, right-angle thick sheetmetal brace, running front to back (parallel to the TM length) under the center of the tank. I had to custom -make 2 very stiff metal braces that i attached to each side of the long brace, then bolt these to the even-thicker frame material above and near each end of the tank. The repair withstood a 30 gallon fill to capacity, no leaks. I could see the 36-inch brace bowing under the pressure of that much water on the bottom of the tank, then it returned to straight after dumping the water. An I beam type brace would provide more support. Traveling far with a nearly full tank, after boondocking and enroute to a dumpsite, may have been the straw that broke the camel's back, causing the cracks to advance toward leak stage. So for prevention, I will try to dump ASAP in future trips! Charlie