Anyone have experience with a Little Giant 4MDQX-SC

[smokiums]

I'm having a problem. I believe my pump is sucking large amount of micro bubble into my tank and I think the leak is coming from the connection between the pump and the bulkhead. What I'm trying to find out is if any out there has a similiar set up. I have the little giant 4 connecting to a 1inch bulkhead. The problem is that I couldn't find the proper adapter to screw into the pump and screw onto the bulkhead. They both have different threads.

If anyone out there found the correct adapter, please let me know. Or if you have the same problem and solved it, please help me.

Thanks.

 

[loganj]

If I remember correctly, and it happens sometimes, the MDQX4 has 1" female inlet and a 1" male outlet. If your bulkhead is threaded on the inside, as most are, you'll need the following PVC fittings to make the connection starting at the bulkhead. 1" male adapter-piece of 1" pipe-1" valve (optional)-piece of 1" pipe-1" union-1" male adapter. I'm guessing what you meant when you said the threads were different is that both the bulkhead and the pump are female? You'll want to use teflon plumbers tape on all threaded connections. Be sure you wrap the tape in the direction that the fitting turns when you tighten it or it will strip all the tape off. Screw the 1" male adapter into the bulkhead. Glue in the short piece of pipe. Glue the valve on. Glue in another short piece of pipe and glue the union to it. The valve is optional, but it allows you to quickly remove the pump without draining the sump if you need to. Another short piece of pipe coming out of the union and the other 1" male adapter on the end of it. Take the union apart and, after applying the teflon tape, screw the male adapter into the pump. Put the union back together and you're good to go. Both the pump and the bulkhead should be 1" NPT (National Pipe Thread). HTH.

 

[smokiums]

Logan, thanks for taking the time out to write this awesome email, however, the threads are a little different. The pump side is a female inlet and the bulkhead side is male inlet. The problem is that there both different threads. The bulkhead has very thin threads and the pump side threads are spread out more.

How about using plastic tubing?

 

[Sam]

I have this pump with my set-up and have no problem with the threads on the fittings, they are NPT standard. If the bulkhead threads are a different pitch, then that must be a non-standard fitting. However, on the issue of microbubbles. My set-up uses a 1"MPT - 3/4" barb fitting and this is what returns back to the tank. This acts as a bit of a choke or restrictor on the inlet side. I think that if you are running 1" in and out, sump is not returning water fast enough for the pump, causing it to pull air into the intake. Also make sure that you have a high enough water level in the sump when the pump is running or for sure, it will pull lots of air. It should be at least 2-3" about the top of the intake bulkhead. If you look very carefully at the intake bulkhead when the pump is running, you should be able to see if it is pulling air from the surface of the water. You will see a little vortex of air cycloning down to the bulkhead. HTH 8)

 

[smokiums]

I do have the return converting to 3/4 inch. The flowover comes down at 1 inch. I also have a release valve coming off the return that I have running back to the sump, for additional water for the pump. I'm not sure whatelse to do, but remove the pump and try all new plumbing to the bulkhead or see if LFS sells different threaded bulkheads.

Is there a place online that sells bulkheads?

 

[Sam]

There are a bunch of online stores including some of the more popular on-line fish retailers. In addition, your local LFS should stock this routinely if they are large enough. How is the static water level in your sump when the pump is running?

Here are a couple of places that sell bulkheads:

www.plumbingworld.com
www.drsfostersmith.com
www.usplastics.com

 

[smokiums]

What do you mean "static water level"?

 

[Sam]

I am sorry, let me back up. Do you use a sump for your return or do you have the pump connected directly to the return line from the tank?

 

[smokiums]

There's a compartment at the end of my fuge that the pump pulls water from.

I'll try uploading the layout to my gallery so you can better understand.

 

[Sam]

That would help, but I get the feeling that you do not have enough standing water to feed that pump. I am using that same pump for my 135G tank. the return goes through an overflow into a sump that when the system is running, holds about 4 gallons of water. This is what the pump draws from so there is always an adequate supply of water for the intake. Unless you have an oversized return for the fuge, I do not think you are feeding the pump enough water. I would definitely consider resizing the pump for your set up.

 

[smokiums]

I have about 110 gallon of water between my main tank and fuge. Between the two, I have about 110 gallons of water.

The return area of the fuge is about 4inchs wide, 12 inches deep, and 12 inches high. It was about 2 inches wide, but I decided to add the additional divider between the fuge and return. I also branched the return going back up to the tank with another valve which I flow back into the return part of the fuge. So, not all the return water that the pump is sucking is going back up to the tank, some of it gets dropped back into the return for additional water. I can re-plumb the exhaust valve to go back the beginning of the fuge if I want, but that's the same as what I am already doing.

btw...the layout is now available.

 

[Sam]

Okay just to clarify in my mind. Your main tank has an overflow box?
That main tank overflow output is sent to your fuge?
Your main pump's inlet is conencted to the output on the fuge?
The main pump return is split between a return to the main tank and a return to the fuge?

Some Questions. (When the pump is running):
the return area of the fuge where the inlet for the pump is connected, what is the water level?
Is the water going to the pump swirling down the inlet to the pump?
Do you see any eddys of water being sucked down?

 

[smokiums]

Yes.
Yes.
Yes.
Yes.

1. I have to use the split most of the time to keep the water level high, but I keep it at about 4-5 inches.

2. The water falls from the fuge into a small divided area and flows under that wall into the return area. You can probably see it better on the diagram.

3. The bulkhead has a 90deg elbow pointing downwards in the return area with a foam around it. The foam, so that bubbles don't go main tank.

I hope this all makes sense.

 

[Sam]

Couple of things, I would take the foam away for starters. Nothing should obstruct the inlet to the pump. That could also be contributing to air bubbles. Secondly, how much water is in the return from the top of the 90 deg. bulkhead to the surface of the water?

 

[fishfreek]

I have this pump and i must first applogize as I have not read all the posts in this thread like i normally do.

What i had to do to remove the microbubbles from the pump was put a hard plastic pvc connection between the sump and the pump and make sure nothing was restricting the flow between the sump and the pumps impeller. THe microbubbles I was getting was as a result of cavatation of the impeller.

My first setup used a clear plastic tube and the suction from the pump basictly clamped the tube down to where it was restricting flow to much between the sump and the impeller.

I also have to keep my water level approx 4" above the sump bulkhead else the pump will create a minicyclone pulling in air from the sump.

 

[Sam]

That is what I am thinking is causing the problem. This is a pretty powerful pump and as you noted, if the water level is not high enough, it will create air funnels. I use clear tubing and I think that with the 1" tubing there should not be a problem unless the run is too long. Hope this all helps "Smokiums." 8)

 

[smokiums]

Man, you guys are awesome.

Well, last night I received my order of aqualcultured liverocks from LIVEROCK.COM, which was wonderful. Lots of live, probably over 7 live crabs, a couple of snail and ofcourse, a couple of bad straggler...mantis shrimps. Thank God I layed everything out of the floor before loading into my tank. During that installation and friend of mine came over and we started playing the return valve and exhaust valve to see if we could solve the problem that way. It worked. We reduce the water flow going back to the tank just a hair and opened the exhaust up a bit, just enough to keep about 4inches of water above the bulkhead. This morning, NO MICROBUBBLES. I'm so happy. I can finally enjoy my tank without watching it snow inside my tank. For right now, I'm going to leave the tank as is, but in the very near future, I'm going to do what fishfreek suggested.

Thanks for all the help guy. I really appreciate it.

 

[Sam]

Awesome, glad we were able to figure it out. Remember to factor in evaporation loss, unless you have a top off system. So leave enough "head" water so that you do not start pulling air again if you do not have a chance to top off. What I did is put a mark on my sump where the water head should be that will give me at least a couple of days of no bubbles. As soon as I get my top off unit, this will cease to be a problem (thank heavens), as I lose about 1G a day of water. I think this is also because I had to install two cooling fans in the canopy to help pull off the heat output from my VHOs. Anyway I am happy that we were able to identify the problem.