Mag 7 too much from my wet/dry system?

[wrkalot]

We picked up a MagDrive 7 (for the sump), a 100A Top Fathom Skimmer, and a MagDrive 3 for the skimmer.

The return pump is a AquaClear 802 PH that has been there (and running) for about 6-7 years and the flow seems pretty weak to me so we were going to use the Mag7. Got the pumps switched out and fired up the new Mag7. That thing really cranks! The problem is that my overflow can't keep up with it. More water is being pumped into the tank than is able to flow out.

The large hose that runs from the bottom of the overflow box, on the back of the tank, to the sump has a fairly large dip in it so water flows out of the box, down near the floor, then back up about 7-8 inches to the sump. I'm thinking that that is the problem. If I shorten the hose to eliminate that "dip" the water will have more of a straight shot down and it should increase the flow. Does this make sense or is the Mag7 just to darn powerful?

My other option would be to use the Mag3 for the sump and the Mag7 for the skimmer?

[loganj]

You might gain some flow by shortening the hose, but I don't think it will be a significant amount. You could put a valve, preferable a gate or globe valve, on the pressure side of the Mag 7 to choke it down a little. Or, you could put a T fitting in the line. Run one line off the T up to the tank. Run the other one back into the sump and put a valve on it. That way, you can use it as a bleed line to cut down on the amount of water being returned to the tank without choking the pump back. If your skimmer works with a Mag 3, I very much doubt it will handle the 7.

[wrkalot]

Well, the 7 is one the pumps the manufacture recommends for this skimmer

Recommended Pumps: Rio 2100, Rio 2500, Mag-Drive 5, Mag-Drive 7, Little Giant 2MDQSC, or Iwaki 20RLT

The lfs store is the one that recommended the Mag 3... they are also the ones that said the over flow would be fine with the 7 as the return pump. I thought it would make more sense just switch the two. I think I'll call the skimmer manufacture to verify the info.

[wrkalot]

The manufacture just called and said the Mag Drive 7 would work fine so I'm going to swap them out tonight and see if it all works. If not I'll be back for more details on the gate valve idea.

Thanks for the help!

[fishfreek]

What is the size of the drain line on your overflow? If the drain line is 1" then it should have no problem handeling the flow of your mag7. And as logan mentioned the dip in the drain line is going to be slowing it down some as the water has to go up aganst gravity.

[wrkalot]

I'll have to take another peek at it but I would guess it's AT LEAST 1". I've seen pictures of systems that have 2 hoses and I assume those are for much larger systems than mine. Maybe I should shorten the hose tonight and try the Mag 7 again? If it is still too much I'll swap the pumps.

[loganj]

My mistake...I was assuming that your skimmer called for a Mag 3 pump. If the skimmer manufacturer calls for a Mag5/7 size pump, I expect the performance of the skimmer would not be good at all with a Mag 3.
Also, if your drain line is at least 1", what about the siphon tube? I'd think you'd need at least an 1 1/4" to handle the flow of a Mag 7.

[wrkalot]

Well, the siphon tube is not that big... I don't think. I'm headed home soon and will get the exact measurements and post tomorrow.

[wrkalot]

Forget everything I posted above because... I am an IDIOT ! A few days ago I put a bag of Nitrate Rocks/Sponge in the wet/dry and it was restricting the flow causing the display tank to over flow *Doh* Removed that and everthing works. Of course it took me an hour and a half last night to figure it out.

I have the 3 for the return and the 7 on the skimmer and things are cookin'... so much so that it's quite loud. I guess I shouldn't be suprised that a 7 year old 802 PH has lost what ever oomph it had.