wrong 1 pump 1 timer gravity will let the water flow back into the res when it kicks the timer off
Actually, I would say YOU are the one that is wrong, not them...
If you only need 1 pump and 1 timer, than you do infact, NEED 2 of them..
why? protection against failure... its that simple..
If you have 1 pump and timer, if EITHER fail, and your not around fairly quickly, your plants suffer..
Have 2 pumps, on seperate timers, and it's much safer for protecting your plants against a pump or timer failure.
NEVER use the bare minimum to make it work, ALWAYS double-up on vital equipment, incase of failure. telling people they are "wrong" for such practices shows your ignorance and inexperience.