Could multi-port valve gasket leak cause loss of prime?

[Desmond.TFP]

My pump ran dry twice this week, second time I could not get it re-primed. The pool service guys came out and diagnosed a leak, probably gasket, at the multi-port valve and I could see a water leak out the backwash pipe once we disconnected the hose. They scheduled a repair, but got the system primed (after considerable difficulty) and apparently running ok, and asked me to leave it on 24x7 until the repair tech came out a couple of days later to fix or replace the multi-port. The pump had run dry again by next morning and pump seal got damaged.

Repair tech came out again, opened multi-port, found some roofing granules in there what were likely causing the leak, and cleaned it out. Tech says the multi-port leak could not have caused that last loss of prime and pump seal damage. He says once system was left on in 24x7 mode, the only things that could cause pump to run dry are (a) pool water level was too low (which he now says was my responsibility to check & ensure), or (b) we lost power and system switched off, lost prime, and came back in auto mode.

Question: Is he being straight with me?

 

[1poolman1]

Likely, yes. Any where air can get into the system with the pump off will allow water to flow back to the pool, either from the filter or backwards through the suction line (pump). A pump is "primed" if it has water in the pot up to the bottom of the suction port. You may have two issues, not uncommon. While the leak at the MPV could allow air into the system as the equipment drains (think lifting your finger off the end of a straw), the pump running "dry" cold have overheated the inlet plumbing and caused it to shrink a bit. This will allow it to suck air in place of water and never completely be able to move sufficient water t provide a continuous flow.