Recently replaced my prematurely failed 6 volt batteries. Apparently, they had not been maintained by the dealer during my coach's long wait for a good home.
Checked with the factory for an 05 battery water system; ~$300.
Saw the Pro-fill battery water system at Camping WOrld on sale for ~$50 (3 each for 6 batteries) plus an $18 pump. Decided to buy it.
Install was simple, parts seem well made and I was able to route the water feed tube around the battery case, so topping off water doesn't require removing the box; pretty quick and simple.