The idea that I had for the holding tank was just to plumb a pump to it, and once it was full, pump it out to the sprinklers. I've already plumbed the sprinklers and tested it with the sump... but sumps are low pressure, high flow, so I didn't stick with that setup. Didn't want to burn up the sump... that would be bad. Probably just get a 55 gal plastic drum, pump from the sump to that. Have a float on the drum. When that fills up, kick on the other pump, and run it out to the sprinklers. Ran into some cost constraints with this setup though. Figured I'd need a directional valve to divert the flow of water to the holding tank when it got full to somewhere else. Those can't be cheap... I haven't even sought out for one. I guess I could rig up something like an Asco valve that could do the trick. And the cost of another pump that will output ~ 40 psi (which I think is about our city water pressure) to run the sprinklers was another inhibitor. You're right though, a water sump pump does offer peace of mind in case of power outages, and with a newly finished basement, I'll have to seriously consider one. Guess I'm looking to see how much water I pump out on average to get a good idea on how often my lawn could be watered.