Closed loop pump

[Magnoliamg]

Hi all.. I have been a lurker for awhile...always planning to jump in but never got the chance to . Now I've hit a problem with my tank that I need some assistance with. All of a sudden, after almost 4 years, I'm getting micro bubbles out of my closed loop. I couldn't really tell if it was debris or bubbles so the first thing I did was to remove the intake tube and clean it really well. Man, it was really clogged up (I had never cleaned it.:squigglemouth:) I thought while that was clean I would go ahead and clean out my OM 4 way. Put everything back together.. no leaks and turned the pump back on.

First couple of minutes.. all went well... then the bubbles came back. I turned the gate valve down leading to my pump and the bubbles went away.

Has anyone had experience with a pump going bad and creating bubbles?

Here is my setup:
240 DT
75 gallon sump
Mag 24 return
Blueline pump with OM 4 way for the closed loop.

Any help would be appreciated!! :bigsmile:

 

[mr_X]

i don't have experience with that issue, but logic would tell me that there is a tiny leak somewhere. inside the pump, in the plumbing....do you see any salt creep anywhere?

 

[Magnoliamg]

Salt creep

No dripping or salt creep anywhere. That is why I first thought that it was debris getting into the lines. This is so strange.

 

[AZDesertRat]

Have you cleaned the pump? Its possible you have restrictions/build up in the pump volute or impeller area.
If you need to restrict or throttle flows always do it on the discharge side of the pump, never restrict the suction or intakeas this leads to cavitation and microbubbles.

 

[Magnoliamg]

Ya know.. I didn't clean the pump.. just turned the gate valve down at the output side. I'll pull the pump out tonight and clean it really well. Thanks!

 

[AZDesertRat]

Take the pump apart and soak everything in a 1 gallon plastic pail with straight distilled white vinegar for an hour or so and it will be as good as new. Vinegar is about $1.50 a gallon at WalMart and works great. I strain the big chunks out with a paint strainer or pour it through paper towels or old panty hose and re use it until it loses its strength, lasts at least a year that way if you don't dilute it with water.

 

[Magnoliamg]

Cool... I bought a case of vinegar a couple of months ago from Sams to use for staining concrete... guess that I will break into the stash and use it for the tank. :)

 

[mr_X]

but where would the air come from? i recently broke down a closed loop with a reeflo barracuda, that i had running for 3 years straight without a single cleaning. it never produced bubbles.

 

[AZDesertRat]

When a centrifugal pumps impeller spins it creates a low or even negative pressure area at the eye or center of the impeller. It is possible to pull air out of solution in water given the right conditions, this is why you never want to restrict the intake of a pump which causes a starved condition then expands again as it is pumped out making the bubbles visible.
If you read up about cavitation it can do some wierd things you wouldn't think possible

 

[mr_X]

interesting. thanks.

 

[Magnoliamg]

Well, I pulled the pump apart and found that it was not only air bubbles but shavings of a shell. There were 2 small shells stuck in the impeller and once I got them out, cleaned everything up and put it back together everything is great again.

One huge thing that I noticed.. the pump was so dirty inside that I was loosing gph from the pump. I forgot how much flow came from the closed loop. LOL

 

[Magnoliamg]

forgot to say... Thanks AZ!!

 

[Mr E Wrasse]

Nice fix! then it was the cavitation from the impeller. I was just watching a special last night discussing cavitation in submarine propellers. CRAZY!

 

[AZDesertRat]

I make it a point to soak all my pumps in vinegar 3 or 4 times a year. You are right, you really don't notice how much the flow drops off since it happens over a long period of time. When the pumps are nice and clean the flows are always more.