Driving skimmer direct from overflow?

[ira_one2]

Hi,

Anyone drives their skimmer directly from overflow? (Main tank -> overflow -> skimmer -> sump). Thought of doing this to lessen the heat generated by PH as well as to save 1 power point.

Pls comment on the following assumption:

- Using 5000 l/hr to pump water back from sump to main tank. So, flow rate from overflow to sump should be around 5000 l/hr as well.

- More skimmate due to no filtration (now I'm using wool and other stuffs).

Thanks in advance.

Cheers,

[bwilly]

5000 is too much. your skimmer confirm get over skim..

lucky if u can get teh-o..

if not every time sky juice..

u can try T off from return pump to the skimmer..

u must remember to ensure while T off at that cut off section.

100% of the water goes thru your skimmer..

one mistake of mine when I decide the T off..

I use my return to run both my skimmer.. so far oki..

one pump run return n 2skimmers..

[riot]

Hi!

You are using a PH to deliver water from your main down to your sump? Tecnically, no issue there to drive your skimmer, but the problem will be when your return fail, and your main2sump pump continue on and overflow your sump.

[riot]

oops I got it. sorry wrong info.

[bwilly]

tik he meant return pump back.. overflow how back down cannot skim..

he rephrase wrongly on the first sentense.

[ira_one2]

bwilly,

I'm not going to drive the skimmer from the return pump but from the overflow (main tank -> sump). My plan is to T off and use ball valve to control water intake to skimmer.

Cheers,

[bwilly]

bwilly,

I'm not going to drive the skimmer from the return pump but from the overflow (main tank -> sump). My plan is to T off and use ball valve to control water intake to skimmer.

Cheers,

something like those waterfall generate electricity..?

I am not too sure on this area..

but I can see some cons..

1) all the junk n stuffs get into your skimmer.. choked easily.

2) your water flow back to piping sufficient to pump your skimmer..?

return flow back to your tank possible since its pressure force back.

over flow back not so.. base only gravity pull.. plus the T off n joint, come back bo power liao, so I wonder enuff bo.

[blueheaven]

well it really depends on which type of skimmer you using but I would love to see it in action :lol:

[AlfaRomeo]

I think there such things like down-draft skimmers which uses the smae concept.

Basically you cant power force-injection or beckett style skimmers but those lower flow skimmers like H&S should work fine with the return flow IMHO. Bubbles are created separately thru a recirculating pump rite?

[bwilly]

maybe.. but if it does not work.

make sure u make prudence steps that allows u

to remove the skimmer piping n resume normal flow.

its a risk I won't take.. alot of problem.

[ira_one2]

All,

Thanks for the response.

Just to clarify, I'm not planning to build a downdraft skimmer and create waterfall effect with the water going into the sump through a tower of bio-balls. Just thinking of driving my cheapskate venturi skimmer directly. Plan is to T the pipe from overflow and adjust the flowrate into the skimmer using ball-valve. Definitely will do trial and error to get correct adjustment...

Cheers,

-

[bwilly]

All,

Thanks for the response.

Just to clarify, I'm not planning to build a downdraft skimmer and create waterfall effect with the water going into the sump through a tower of bio-balls. Just thinking of driving my cheapskate venturi skimmer directly. Plan is to T the pipe from overflow and adjust the flowrate into the skimmer using ball-valve. Definitely will do trial and error to get correct adjustment...

Cheers,

-

ya I know. I agar agar believe u r talking abt that..

hence my two points above on the cons..

but remember you are not using any filter material..

all gunks will get into your skimmer.

u decide in the end, but update us of your work..

good luck.

[Eric]

All,

Thanks for the response.

Just to clarify, I'm not planning to build a downdraft skimmer and create waterfall effect with the water going into the sump through a tower of bio-balls. Just thinking of driving my cheapskate venturi skimmer directly. Plan is to T the pipe from overflow and adjust the flowrate into the skimmer using ball-valve. Definitely will do trial and error to get correct adjustment...

Cheers,

-

Your overflow will not be strong enough to run the venturi effectively cause the only energy it gets is from gravity, not sufficent to suck in the air from the venturi........it will work however if you direct the overflow to the suction of a pump or if you use a recirculation needlewheel skimmer like the H&S then you can control the flow into skimmer and yet get enough air bubbles from another needlewheel pump.

Eric

[bwilly]

Your overflow will not be strong enough to run the venturi effectively cause the only energy it gets is from gravity, not sufficent to suck in the air from the venturi........it will work however if you direct the overflow to the suction of a pump or if you use a recirculation needlewheel skimmer like the H&S then you can control the flow into skimmer and yet get enough air bubbles from another needlewheel pump.

Eric

he wants to save one power point..

so using another skimmer who r running on another PH, no cost savings for him..

[ira_one2]

Anybody here usinf downdraft skimmer? Pros and cons?

[ira_one2]

Sorry... please disregard the last question. Will post in other forum.

[Domino]

Hi!

If you're planning to use a standard venturi skimmer, it will never work I think.

What drives a venturi skimmer ir not just the flowrate, it's mainly the pressure your pump can deliver.

I might go a bit off-topic , but I'll give you a few explanations about pumps...

Any pump is defined by two key parameters:

-the flow rate measured in volume of water (liter, gal, m3...) over time (hour, second...) this parameter is easy to understand

-the pressure of the pump measured in the "height of the water column" it can support. In other words if you put a straight pipe at the output of your pump, how high can it pump the water if there are no losses in the pipe (there always are losses!!) The diameter of the pipe does not matter, only the height of water puts the pressure (in fact, the bigger the pipe, the lower the losses!!) A good analogy is that you can be 5m underwater in a swimming pool or in a large fresh water lake, the pressure you feel on you ears is the same: 5m of water column pressing on your ears; the surface does not matter!. As the pressure of the pump is expressed "height" the pressure will usually be a distance unit (meter, cm, ft...) you can check on your pump, most good PH or pumps indicate both measures but the pressure is often overlooked.

Obstacles to the easy waterflow such as an elbow in your piping, a change in pipe diameter, a venturi (very strong obstacle!!) all lead to pressure loss and this pressure can also be expressed in equivalent "height of water column". For example an elbow creates a 35cm loss , 3m of piping create 30cm loss due to friction, a venturi+ skimmer might cause 1m loss (just a guess...), passing through a chiller leads to losses... (in physics, this is Bernoulli's principle)

Basically, the rated water flow of a pump is given at point 0, just at the exit of the noozzle. From that moment on, losses keep reducing the flowrate. there is an almost linear relationship between flowrate and pressure to overcome (the good pumps even supply a graph of the realtionship; check some boxes and manuals in shops...)

You can actually do the calculation of what min return pump you need for your sump:

- by measuring how high the water has to be pumped up from the sump to the tank (ie: 110cm).

-say you got two elbows (ie: 2x25cm= 50cm)

-and 1.5m of pipe (ie:15cm).

So the total pressure to overcome is 175cm (setup losses).

Say the pump you want to buy has 3000L/h and pressure of 3m. this means:

- 3000L/h @ 0m loss

- 0 L/h @ 300cm loss = max loss

so what is L/h when losses are 175cm? the formula below is basically the formula of the line if you plot the two point above

actual L/h=(L/h @ height 0) - [(L/h @ height 0) /(max loss) ] x setup losses

in this case:

L/h= 3000 - (3000/300) x 175 = 1250L/h actual expected flowrate...

So when you buy a 5000L/h pump for the sump, it does not mean you get 5000L/h flowrate in your system...

seemingly (getting back to the topic ), when you plan to use the pressure of the falling water (basically the 110 cm height less pipe& elbow losses) you are going to get a very low pressure and flowrate to operate the venturi. A strong pump needs to be BEFORE the Venturi to make it work.

I got carried away a bit . I hope this was helpfull and not to boring ...

cheers!

[ira_one2]

Domino, great explanation. Thank you for the detail. Not only it clears this matter but other matters I have.

Bwilly, agree with your points. The venturi can easily get clogged.

Cheers,

[riot]

To save power, I think it will be easier to mount a skimmer above your tank, run the return from the sump into the skimmer, then the output of th eskimmer into the tank. Voila! 1 pump to rule them all

And...... if you run a chiller, run that thru as well! Of course, with the restricted flowrate and all that it might not work, but still an interesting idea.

[ervine]

I thought of using the return as well.. but the problem with returns is that it's half air half water... and when big bubbles from the return enter your skimmer chamber it basically makes it completely useless.... big bubbles disrupt the formation of foam...

[Tanzy]

Skimmer output directly into tank = microbubbles everywhere.

Downdraft skimmers require high water velocity so gravity won't be sufficient to drive it. They need pressure rated pumps to push water through a nozzle aimed at the bioballs.

[Navyblue]

The idea of plugging overflow outlet to the inlet of the skimmer does not work. Tried that before and let me tell you why.

1. The flow from the overflow is inconsistent and often mixed with air. A skimmer need a consistent flow to work properly.

2. I tried to throttle the outflow with a valve, I managed to make the flow consistent with no air in it, but the overflow is not fast enough to cope with the return pump (for my case), and accumulation of water in the main tanks occurs.

3. Some skimmers like Weipro skimmers has a significant constriction in the venturi that makes the passage very narrow. A downflow from overflow do not have the high pressure from a pump, thus the overflow will be greatly slowed down and making water accumulate in the main tank. When using pump to drive a skimmer, the outflow of water is lower than the flowrate of the pump due to the constriction. When you are driving 5000L/H up to the main tank and you get 5000L/H down as there is no resistance. But if there is resistance, the downflow will become lower than upflow and your tank can get over flow.

[ira_one2]

Thanks Navyblue. Got your message on accumulation of water in main tank....

Cheers,