First, it is important to layer a cotton mattress pad on top of the wool moisture pad. What you would see, after you pour water on the wool moisture pad, is that at first the water beads up, but after a while, the water would eventually leak through. However, when you layer a cotton mattress pad on top, the moisture is absorbed into the cotton and isn’t puddled up on the wool moisture pad. This seems to be very effective in keeping moisture from soaking through the pad and into the mattress. If you find an accident, all you have to do is wash the cotton mattress pad, as you will find the wool moisture pad and the mattress underneath to be dry.