Mag Drive pump sucking air at outlet?

[cjburden]

I'm trying to figure out what the deal is. I have a Mag 9 plumbed externally setup as my return from my sump. When I turn the pump on it sounds like it is sucking air from the outlet and I have many microbubbles in the tank. The outlet is 3/4" mpt with a 3/4" mpt x slip coupler attached.

I used Teflon tape on the threads of the pump and screwed the coupler down hand tight. After a week or so I decided to try to use additional Teflon tape to see if that helped and of course it didn't. I'm not sure what I should do about this, I thought about just smearing some silicon around it but perhaps someone has a better idea.

 

[APISTOBORELLI]

Too much tape may put a small crack in the housing. I've had to replace them for that reason.

 

[Jim Tansey]

The outlet is the pressure side, I can't see how it would ever "suck air" are you sure its not a leak on the inlet side? On another note, a Mag is a poor choice for an external pump.

Jim

 

[cjburden]

poor choice is a good way to describe it, I'm a man on a budget and it was cheap hopefully I don't wind up just replacing it.

would I be better served simply moving it in sump? I'm relatively sure it is not from the inlet side. When i cup my hand over the outlet the noise changes vs over the inlet it doesn't.
I guess I'll have to check for a crack later on. though I didn't see any earlier (but I wasn't looking closely for cracks).

Also I basically don't have any clue what I'm talking about here, but I would think if it WAS sucking in some air it would be from a microscopic gap between the threaded outlet and the coupler. The water leaving the outlet would create suction on that gap and allow microbubbles into the line. Perhaps I'm way off on that, but that what I'm guessing.

 

[Jim Tansey]

A quick answer is the pump will perform much better in the sump, I have used them over the years and with regular maintenance you will get good service from it, it just is not a good external pump.

Jim

 

[cjburden]

well I think in the sump the water level will be higher than the outlet, so that might essentially solve this issue. Perhaps I'll give that a try, thanks.

 

[JohnK]

Maybe I'm confused here, but if you say it's sucking air at the outlet - do you mean that it's sucking air where the water is being pushed into the tank ?

If so, it's simply because the point where the water is being pushed into the tank is located too close to the water's surface. Lower it a half inch or an inch and the problem will be solved.

I beleive this is roughly because the water coming out of the plumbing is going from being under pressure to no pressure. This change in pressure makes the water suck in air from the surface. (I may be describing the "why" wrong here, but I've seen it plenty of times to know that it happens).

Edit, adding;
if you mean it's sucking air where the water goes into the pump, then YES, either the plumbing has a slight air leak, or the sump level is so low that the suction from the pump is enough to pull in air from above (meaning you need to raise the sump water level).

 

[cjburden]

Maybe I'm confused here, but if you say it's sucking air at the outlet - do you mean that it's sucking air where the water is being pushed into the tank ?

If so, it's simply because the point where the water is being pushed into the tank is located too close to the water's surface. Lower it a half inch or an inch and the problem will be solved.

I beleive this is roughly because the water coming out of the plumbing is going from being under pressure to no pressure. This change in pressure makes the water suck in air from the surface. (I may be describing the "why" wrong here, but I've seen it plenty of times to know that it happens).

Edit, adding;
if you mean it's sucking air where the water goes into the pump, then YES, either the plumbing has a slight air leak, or the sump level is so low that the suction from the pump is enough to pull in air from above (meaning you need to raise the sump water level).

It actually sounds like air is being sucked in from where water EXITS the pump, which is bizarre to me. Outlet of the pump connects to a 3/4" pvc coupler (threaded). At this connection of pump and coupler there is a noise which sounds like air is being sucked in. The water level in the sump appears to be high enough that air isn't being sucked down from the surface. The outlet pipe in the tank is connected to flexible loc-line so I can adjust that as needed and this is not the source of my issue.

 

[willray]

"Sounds like air is being suck in".....follow the sound.If you have a reduction on the outlet and it has a crack then it's possible it could be acting like a venturi.My loc line line constantly has salt creep on the joints,which means water is getting out so air can get in as well.good hunting.