New guy question on pump/overflow combination

Greetings!

Just have a quick question about overflows and return pumps.

It was my understanding when purchasing these items that it was possible to "dial back" the output using ball-valves in the plumbing.

The two pieces I have are a Mag Drive 9.5 (950gph/800@4ft) and an Eshopps PF1000 rated at 900gph.

The overflow has two outputs, with one u-pipe. I have installed one ball valve on each return going to my sump, and then another valve on above the pump returning to the tank.

Should I be reducing the flow on the overflow to the 700gph range to even things out? Or is it OK to have a bit more overflow than return? My guess is that its not the case...

I can draw up an MS paint diagram of how it all is installed as of today if it helps anyone.


Thanks for any advice!

 

One ball valve in the return line is all I use to control the output of the return pump. It just seemed easier to deal with only one adjustment than multiple ones. Gate valves are more expensive, but offer more precise control over the flow of water.

 

do you have a single built in over flow, two corner over flows, or a hang-on-back overflow?

In any event, the valves go on the output side of the return pump(s). putting them on the inlet side will burn up your pump motor.

Valves in the drain line from the overflow to sump is redundant for flow control, and could even cause a system failure*. On the other hand, valves on the drain line are handy to have for a total closure if you need to work in the sump without any water coming back in to it from the overflow - just leave them full open when the system is running.


* say you have an overflow that's natural flow is 600gph, your return pump is valved to return 550gph into a sump of a volume of 20g - the system works fine. Now you throttle back the drain line from the overflow a bit with a valve, thinking you'll slow down the flow... and it's set arbitrarily, but as close as possible, to what you think is 500gph, and you set the return pump to what you think is the same 500gph and watch the sump for a minute or two... level looks normal, you go off and leave it... but what you really did was set the drain to 499gph and the return pump to 501gph. 10 hours later your sump is dry and your pump is burned out.

Hope that makes sense and is what you're talking about... if not sorry, it's l;ate and I need sleep.

-Doug

 

Hi,
If you have the flow set up for more overflow than return, fairly quickly the tank level will drop and overflow will decrease without your needing to do anything. Do all your controlling on the return side, the overflow will follow it. As pointed out nicely above, too much return can drain your sump if the overflow is limited. It can also cause your display tank to flood (if you return so much water that the overflow physically can't keep up. (Clear as mud?)- Paul

 

Thanks guys, I think I remember reading something along these lines a while back when I first started researching this project but this definitely cleared it up (like mud! Hehe).

The valves I installed are AFTER the HoB overflow, and AFTER the return pump. My thoughts were to be able to cut off all flow to and from the tank in the event something catastrophic were to happen, or if i needed to do maintenance on the tank as stated above.

Thanks again for the great replies.... I'm sure I'll have some more questions as things progress. Started filling my first load of RO/DI last night. Woke up to a 40gal trash can totally full this morning before I left for work. Close call!

 

You got great replies here; we have a very similar setup to yours with our Lifereef overflow and MagDrive 9.5. We run a single ball valve and a check valve off our return line but our inlet line is a straight shot to our bulkhead from our overflow. IMO, I agree with the other poster that a ball valve off the overflow is unnecessary. I know our Lifereef absolutely never breaks it's siphon no matter how much you stop & re-start the pump...the Eshopps could be designed similarly. We have essentially the same rated gph setup as yours and we run our MagDrive wide-open anyway (due to line length and headspace).

 

Never throttle the overflow, let it flow unrestricted. All you need is one ball valve on the discharge of the pump to reduce flow. It will not harm the pump in any way, it will probably make it more efficient by adding a little restistance or head.

Avoid check valves at all costs, rarely if ever are they needed with a properly designed return. They are mechanical devices and will fail, not if but when. Keep your returns just below the surface so they break suction with a very small easily calculated volume of backflow, in my case its 3.8 gallons in a 100G display and I always have that much freeboard in my 30G sump.

 

I just noticed that your Eshopps overflow is a dual inlet model, rated at 900 gph. As a point of reference, our Lifereef is a single inlet rated at 600 gph, we also lift ~4ft or so too, and we are running our MagDrive 9.5 wide open. My experience with system setup is admittedly limited, but personally, IMHO, I would have considered stepping up to the next MagDrive model.

I agree with all of these statements, and in hindsight, if (more like when, lol ) we do another setup, we'll likely skip the check valve. But we used a high quality true union swing check valve, and it works well for us.

 

Well, I finally got around to filling the tank and getting all the leaks cleared up (overflow outlet o-rings were crappy). Strangely enough its looking like the return pump is out performing the overflow. The only way I could get the system in wide-open to balance was to fill the sump until it balanced, which left an uncomfortable amount of water in the system (when I shut off the pump, the sump filled to the brim.)

If I'm reading the signs right, i think i need to back off on the pump output a little bit so that its not pulling as much water out of the sump. does the hight of the overflow rim (or depth, I guess) have any effect on this? I could lower the overflow box into the tank a bit more to increase the amount/rate going into the overflow perhaps to boost that flow to the sump?

Any thoughts would be great!

 

you should not have any restriction of flow from overflow back to sump - could lead to flooding your DT.

it doesn't sound like you do, but just to reiterate, you should not have any restriction on the intake side of your return pump (ok to have valve here for maintenance, but should be all the way open when pump is on)

you should use ball valve on return side of return pump (between pump and DT) do limit return flow until it's balanced with the overflow's capacity - turn pump on, dial down flow with this valve until water level in DT stays steady.