View Full Version : Testing my Eheim 1250 & Overflow ...

04/26/2006, 07:32 PM
I've got an Eheim 1250 pump and a Lifereef siphon overflow waiting to go on my 37g as soon as I get around to finishing up my sump. I have a 3/4" U-tube for the overflow. Because of the smaller diameter, the water will flow through it faster, thus helping to prevent bubbles from building up in the tube which could cause it to loose its siphon. Now keep in mind, I'm not trying to push 600 gph through the overflow, I'm just looking for something in the 180-200 gph range. I believe that the Eheim 1250 should be capable of this ... So I'll set up a little test in my garage and see how it does.

Okay, here's the setup:

Old Oceanic Salt bucket for a water container
Lifereef overflow with 3/4" U-tube
1" PVC return into the bucket
Eheim 1250 pump with standard hose attachments
4 feet of 1/2" ID / 5/8" OD Vinyl tubing
1/2" hose/PVC connector
3/4" PVC return (about 3' tall, with two elbows)

I set it all up so that the overflow was about 53" above the pump (within 1/2" of the height of my tank) so the headloss from this test setup should approximate what I'd see when it's on my own tank. Right? Anyways, here's some pictures of the pump and siphon in action:





Overall, it seemed like the 3/4" U-tube was able to keep up with the Eheim 1250 pretty well, just as I'd expect. I figured I'd better try to measure what my flow rate was. So I just removed the return pipe from the bottom of the overflow and held a bucket underneath, making sure I didn't spill water all over :D . By timing it to see how long it took to fill the bucket with 2 gal of water, I figured out that I was only getting ~147gph! :confused: I was expecting a little better flow rate than that!

Any ideas on what I can do to get the flow rate up? Is this really what I should be getting from the 1250? When I put the pump on the tank, I'll hard plumb it with an adapter going from the 3/8" BSP thread on the pump up to either 1" or 3/4" PVC. How much difference would it make if I cut the 4' of tubing on the setup now down to about 2' or so?

04/26/2006, 08:11 PM
The RC head loss calculator on the home page shows a 1250, with 4.5' (54") of head pressure, all 3/4" pipe, and only 2 90 degree elbows has a flow rate of 165 gph, so it looks like you are just about right with your calculations. Changing your tubing to 3/4" will help a *little*, but not much.

04/27/2006, 03:32 AM
I believe that the headloss calculator on RC is based on the information in this Advanced Aquarist article (http://www.advancedaquarist.com/issues/jan2003/featurejp.htm). The nice thing about this article, is that it contains a downloadable Excel spreadsheet so you can do your own headloss calculations when you're not online. Also, you can put 1/2" pipe into the spreadsheet ...

Using this spreadsheet with 4.5 feet of 3/4" pipe with the same static head (4.5') it says I should be getting 166 gph. If I change that 3/4" pipe to 1/2", the flow rate drops to 145 gph. I guess the pump curve for the Eheim 1250 is pretty accurate! If I input 1" pipe, the flow rate comes back as 173 gph.

What I had for my little test was 4 feet of 1/2" tubing, then about 3 feet of 3/4" PVC. If I use 4' of 1/2" pipe, with a static head of 4.5' (using the spreadsheet to do this), I get a flow rate of 146 gph. This is remarkably close to my "measured" 147 gph. I guess that the 4' of 1/2" tubing dominates the fluid losses and that the expansion out to the 3/4" PVC doesn't really do much to the flow.

Looks like I definately need to go with 1" PVC since I need to have more than 160 gph. I figure that as the plumbing slimes up over time that the flow rate will only decrease ...

07/07/2006, 07:21 AM
i thought i heard that the eheims didnt loose much head pressure, thats why i got the 1250 vs. the 1260 because i didnt think my megaflow could keep up, now it sounds as if im only going to have about 160 gph with 3/4" return???

07/07/2006, 08:29 AM
I went with the eheim 1260 on my 58 gallon w/ 20 gallon summp. I have a ball valve T off the outlet for the extra flow but I also added some T joints that I can open up the outlet to run other things. right now my 1260 is serving as my return pump but also feeding my skimmer and will soon be feeding 1-2 phosban reactors. So I will be alble to run all of these devices with my 1260 while it also serves as my return pump.

07/07/2006, 09:19 AM
Cool test.

rsxs1212, there really isn't much difference in flow between 150 and 250 with a 3/4" line running into the display. You are not really going to get any display flow from this, it is for circulation between the sump and the tank. The eheims do go down in flow with head pressure. You should be fine with the 1250. I use that on my 90.


07/07/2006, 10:07 AM
Thanks crumbletop

Yeah, there's really no need to have your sump return pump try to provide a lot of flow/circulation for your tank. All you're looking for is a way to pump the water from your sump back up to the tank. For a lot of people, something in the 100 - 200 gph is all you need for a sump return. Of course, if you're going to set it all up so that your return pump feeds a lot of other devices (like what unmc2001 is doing), then you might need a bit more. However, you may be able to gravity feed a few things too (like your skimmer), and that would let you keep your pump size down.

160 gph is all I want/need for my return pump. Everything else comes from closed loops, powerheads, streams, etc. (as the budget allows :D )

07/07/2006, 10:12 AM
i thought i heard that the eheims didnt loose much head pressure, thats why i got the 1250 vs. the 1260 because i didnt think my megaflow could keep up, now it sounds as if im only going to have about 160 gph with 3/4" return???

Eheims are better than a lot of pumps in terms of their flow not dropping off as much with increasing head, but there is still a drop-off. Here is a good picture (http://www.marinedepot.com/aquarium_pumps_eheim_universal_hobby_powerheads_information.asp). The 1250 should do about 160GPH at about 4.4 feet of head, which is consistent with what xchrisjb is getting (and with the head loss calculators).


07/07/2006, 10:42 AM
I am considering gravity feeding my skimmer off my lifereef overflow. Is anyone else gravity feeding off of a hang on overflow and if so how is it working?

07/07/2006, 12:07 PM
yeah i understand its not your main source of flow...i was just hoping i would be able to cycle my tank water through the skimmer a little more than just over twice an hour, i guess it isnt that bad though....i think i will T off the drain to my refugim now instead of my return, that way i can use the ablilty of the overflow to feed the refugim and not take away from the return but then again maybe not

09/30/2006, 12:17 AM
Interesting. And sad. :(

Although it is really quiet compared the Via Aqua 1300 I had, so I'm half happy and half disappointed. QUEIT!!! :)

09/30/2006, 04:18 AM
<a href=showthread.php?s=&postid=7697255#post7697255 target=_blank>Originally posted</a> by unmc2001
I am considering gravity feeding my skimmer off my lifereef overflow. Is anyone else gravity feeding off of a hang on overflow and if so how is it working?

I am gravity feeding a H&S a110 with a lifereef hob overflow box. I am using an Eheim 1250 for the return. So far it has worked great. I do not get any surging in the skimmer, which was my main concer when setting it up.

I have not fed the a110 via a built in overflow so I cant say for sure if having the hob overflow is hindering the skimmers performance. Like i said though, it seems to be working great.