No pic on your post ....... But if the normal 3 way tap, look closely and you should see some arrow heads, line them up so the tank you want lines up with the pump line and your good to go......
Found out that the selector draws a bit of air on my expanda. Bypassing the selector still doesn't solve the problem of hardly any water coming from the tab. Hand pump works kind of fine.
Bunnings has some garden irrigation taps, 2 for about $6 they work fine as a replacement for the 3 way tap when it wears and sucks air.
One of these and a T piece and job done. Taps off 2 ends of T and other to pump....Depending on tank you want, turn one off and the other on.....did it on my old 14.44 worked a treat.
Second that modification. have two on each tank. One each for electric and hand pump. All combinations of water supply available and taps located near tank.
Pulled the pump out and found a lot of red dirt (wonder where this comes from ;-), took a bucket of water and looked how long it takes to pump 5 Liters of water.
2 Minutes! Is that normal?
(I guess pumping that through all the hoses leaves it ending up with hardly any water.)
Ours pump manages 2.5 LPM, all internal parts look ok, no broken or blocked diaphragm.
I saw a lot metal dust around the knob that make the diaphragms move. Maybe that's the reason for the malfunctioning?