Wow, I don’t know what you guys are all doing differently than me, but when my horses opt not to come in and stand out in the unrelenting rain for hours to days on end, I’ve never had [any brand of] a waterproof sheet/blanket that didn’t eventually get wet! And I’ve owned every brand out there from cheap to stupidly expensive (I currently own ~150 blankets). I probably have more Rambos and Amigos (my two favorites) in that mix, but also have a myriad of others (Schneiders, Weatherbeeta, Shires, Pessoa, Tough-1, and so on). Will also note that my experiences with blankets have been more individual blanket dependent than brand dependent. I’ve had varying waterproof levels on identical blankets more than a few times.
I’m in the minority, but I’m with the CSR on this. If you have blankets that keep the horses dry you’ve either got periodic rain, horses that come in for periods, or horses that are warm enough that they’re drying the blankets via body heat…ORRR I’ve been insanely unlucky over the course of 300+ blankets. Every blanket I’ve ever owned lets water in through the neck (even on high neck blankets - less so with neck covers, but often still around the neck where it attaches), from the bottom up, or through the seam on the back.
The most waterproof blankets I’ve owned haven’t breathed well enough for daily use and wind up wet because of condensation (and often in the areas where the blankets are less lined)
And then I’ve had some cheap 1200D waterproof sheets (e.g. Tough-1) that seem to make the horses wet underneath regardless of the weather (though the med and heavy blankets I bought at the same time do not - so maybe an issue with the breathability of the waterproofing there too…at least when it’s directly against the skin?). I guess I wouldn’t be terribly shocked to find a horse wet under a rain sheet with no fill and at the same time dry under the part that has fill. I would also be curious about how well the sheet would work if you threw a light sheet/cooler underneath when the horse was out?
The only thing I disagree with the CSR on is the idea of throwing it in the washer/dryer to “revive” the waterproofing. That seems to be the kiss of death for waterproofness in just about everything I’ve ever washed. Like others have mentioned, I line my blankets up on the fence in the summer and power wash everything.
OP - was your horse cold? I guess my feeling is that as long as the horse is not cold, I don’t really care if it’s 100% dry 100% of the time. And when my blankets do get soaked, I leave them on the horse (again, assuming the horse is not cold) to dry.