thought I’d share info and opinion on different single point watering systems for lead acid batteries. I work with them and see them used and abused every day. I’m not sure all these companies sell retail, but battery or lift truck vendors might be able to help you out.
1: Philadelphia Scientific BIS
tough as nails, rugged tubing. need special tool to install (just the hole punch) Only one depth. Tubing can be pulled out of place and not fill a cell without any indication of a problem. requires 20 or 30 pounds of water pressure to work
http://www.phlsci.com/
2: Philadelphia Scientific Stealth
low profile, easy installation, works with low water pressure. only one depth. Can have leak problems where the tubing pushes into the injectors. recently developed so I don’t know how well it will last over time. visual indication of ‘full’ relatively cheap
http://www.phlsci.com/
3: FlowRite Millenium
multiple depths available, easy installation. injectors have a tendancy to stick open once in a while if they aren’t vibrating during use. (just tap each injector 4 times with a small wrench before filling to keep them from sticking) somewhat expensive.
http://www.flow-rite.com/
4: BFS
multiple depths available, high profile compared with all the others. visual indication of ‘full’ Annoying to install. Tubing yellows and stiffens with age. fragile compared with the other systems. less expensive than BIS and FlowRite systems
http://www.batteryfillingsystems.com/
For this application, my money would be on the BFS watering system. Flowrite might be a better system but has trouble in some applications. I would get the BFS and install with the longest floats that work in the battery, that way I’d add water more often but would have very little chance of boil-over.