Concrete-free washing machines are lighter to transport, just as good in a spin 9 years ago
"We found it worked as good as a concrete counterweight, stopping the spinning drum from heavily vibrating the machine,"
Sorry to be off topic, but shouldn't it be "worked as well"? Not a native speaker, but it sounds strange.
Very interesting idea, though as many have pointed out, I'd be worried of leakage in the long run. A plastic container should be cheap to replace, however.