The first time I machine washed and dried my chilipad I had one of the tubes rip right after where the tube enters the actual pad. What I ended up doing is cutting a tiny hole in the pad near the broken tube and was able to see that it actually ripped. There was part of the tube still connected to the distributor(?) and then the other part of the tube has a real jagged looking rip. I had to use flush cutters to cut the part of the tube that was still on the distributor and then I cut off the jagged part that was on the rest of the tube, then just pushed it back onto the distributor piece. It was just a friction fit but it's been solid and leak free for ... gotta be 3 or 4 years now. I've machine washed it a handful of times since then. Use the gentle cycle on the washer. The agitator in the washer moves much slower and gentle on that setting, per the name. I've only used top-loaders with it. Not sure how it'd fare in a front-loader.
Also I think one of my mistakes with rolling up the tube and zip-tying it into a bundle before sticking it in the wash. You shouldn't do that because then you have this giant mass that I think is much harder on the smaller tubes attached to the distributor piece inside the pad. I would also strongly recommend not machine drying, just because that's a whole lot of extra stress on the pad. It's quick enough to just lay it across a couple of chair backs and putting the Chilicube on the heat setting. Couple hours tops. Use a hair dryer to help it along if you need to.