New water flow issue

[sheik_yerbouti]

I was moving my tank into the new house (very sweet) and so that opened up an opportunity to restack rock and increase some water flow behind the rock stack. I have a 72g Bowfront with a megaflow and a Magdrive5 (500gph)ââ"šÂ¬Ã‚¦
I built an L-shaped pipe from PVC that could increase the flow of the tank. The vertical part of the pipe runs down near the megaflow and I put a hole in it near the surface of the water to stop the back-siphon in case of power failure. The horizontal portion lays on the bottom of the tank behind my rock stackââ"šÂ¬Ã‚¦it is full of holes to let out a gentle current.
I am running a pump from my sump (below the main tank) up to feed this new pipe.

My problem is that the water pressure in tank is pushing water backwards out of the pipe down into the sump so I have a reverse water flow. This water flow is hard to overcome with a pump because it has to fight the down current before it can actually push outwards.

Is there a reasonable way to fix this? I probably could run a pump from within the display tank but I was trying to avoid that.

If not, I did create increased flow rate to that area of the tank even if it is backwardsââ"šÂ¬Ã‚¦would you just leave it like this?

 

[ReeferMac]

I definitely wouldn't leave it. Sounds like an opportunity for a siphon to empty your tank!
You may need a bigger pump. Mag 5's aren't that big, IIRC? They're also not pressure rated, so... adding a lot of head pressure to a small pump, means very little flow. Sorry.

- Mac

 

[dalbrecht]

I agree with ReeferMac, your "small hole" to break the siphon isn't strong enough. If you have a net flow into the sump, you have a siphon.

 

[Henry Colf]

Is there any way you could incorporate a checkvalve of some sort into the feed line so that the water can't flow backwards?

 

[dalbrecht]

Henry, That still wouldn't address the reduced flow issue, the pump would need to work even harder to keep the check valve open.

Check valves are also prone to failure due to the biofilm that builds up on them.

 

[Guy]

If increased waterflow is the goal then do a closed loop with the mag. It will give you what you're looking for and can't backflow.

 

[sheik_yerbouti]

Thanks for the advice...I don't really want to add a larger pump to the system so I think I am going to take up Gary's advice on the closed loop...safest is good

 

[dalbrecht]

I may be missing something, but if you use the mag for a closed loop, what will you do for a return?

 

[Guy]

If it's the only waterpump then you have to eliminate the sump. I was assuming that there was already a seperate main waterpump for the sump larger than the MAG5. If not then the waterflow is woefully inadequate and you're going to need a much larger pump anyway.

 

[bigkev76]

It doesn't matter what size pump you have as far as a sump size is concerned. you tank is only going to drain to the same level if you have a mag 5 or a mag 18. I would personally replace your 5 with a mag 12 and either put a 1 way check valve and/or drill out your hole in the pvc a little more. Good luck.