vented loops

[fred]

Pegi am having trouble pumping out my holding tank. the problem started when a guest put baby wipes in the head. i had to replace the impeller but the pump will not pick up the waste unless i hold my finger over the hole in the vented loop. should the vented loop be sucking air when the pump is running.

 

[Peggie Hall/Head Mistress]

Sounds like your tank vent is blocked

Although I'm at a loss to understand how blocking the vented loop would help if that's the case (and btw, there's supposed to be an air valve in the hole in the top of the vented loop). What happens when you try to pump out the tank at a pumpout? Do you have a y-valve in the pumpout line...or just a wye or tee fitting?Whether it's the vent or not, I'm 99% certain you have a blockage somewhere...but without seeing what's happening, it's hard to know where.

 

[fred]

Peggie there is a y fitting installed in the system.i didnt have any problem at the pumpout but when using the macerator it will not pick up the waste because the vented loop is sucking so much air.there is a valve in the loop should it be sucking air with the pump running.

 

[Peggie Hall/Head Mistress]

Where IS the vented loop?

Suddenly the light is dawning (I had jury duty yesterday...by the time I saw your question last night, I was brain dead): Your problem has to be one of two things: either you installed the macerator backwards when you put it back after you replace the impeller, or the vented loop is in the wrong place--between the tank and the pump. Those are the only two possible explanations if the pump is sucking air. However, if the macerator were install backward, I don't THINK it could empty the tank if you put your finger over the hole--it would pull sea water instead...so my guess is, the vented loop is in the wrong place. If it's not, then something else is also letting air in...and putting your finger over the hole is blocking one of the sources just enough to let the macerator work.