Welcome, and you are probably thinking you are being ignored. Truth of the matter is likely you are, because likely no-one here is using the cart you speak of and therefore do not have a problem with water getting into the system in the cart they do not have. The question you have is specific, and not likely to pertain to this forum, or its members, which is mostly about compact utility tractors.
Hope we are not coming across as being rude, but you need to seek a different forum for the answer or head back to your Deere dealer.
Sorry.
What tractor do you pull that 'cart' with? Any thoughts as to why water would be getting into the distributuion systems in it?