Help with return pump?

[Nate77]

Ok so I set up a sump in another room , the return pump that came with it was way to loud , yes was on anti vibration mat. Off the recommendation of a couple people ordered a jebao dcp 13000, I can't get enough flow to the tank. Looking at varios and vectras ,don't know if any of them would be enough.
Piping comes off the pump there is a ball valve , and a tee at the top this goes up 15".
From the tee goes across 36" (ball valve in this line also),then an elbow then up 33" then 2 elbow into tank.
Also off this manifold is another tee with ball valve that runs across 67" to a fuge . Lines are 3/4"

Not really understanding how to calculate head height, even tho I understand what it is.

Don't know if it helps but attaching pic of manifold.

The jebao can't get enough back to the tank to get the level in overflow box high enough less then 1/2 full running at 100% if I close the ball valve to fuge I don't gain anything

So I am looking for help selecting a pump ?since this will be number 3.
Must be absolutely quiet, need at least 700gph going to tank. Also hoping to have enough to run reactors and maybe another tank or 2 in the future.


Any help appreciated
Thanks nate

 

[ca1ore]

None of the DC pumps you list handle back pressure all that well …. and based on that picture, you've got a lot of back pressure. Unless you want to redo it all (using larger diameter pipe), something like a Fluval Seas is a better bet. Not adjustable, but quiet.

There are broadly two forms of back pressure on a pump: head, which is the height a pump will have to move water above the sump and friction, which is the degree to which piping restricts flow.

 

[Nate77]

So increasing pipe size will reduce back pressure and allow more flow? Redoing doing the piping I a larger size is no big deal just a PIA.

 

[DCR]

The 3/4" piping is the problem. I would not use it for anything more than about 300 gph. It will be very difficult to push 700 gph through 3/4" unless you go to a high head pump like an Iwaki 70 RLT or Pan World 200 PS. This will be very inefficient due to the high pipe friction. I would increase to at least 1" or even 1-1/4" if you can and the DCP 13000 will probably be adequate.

 

[Nate77]

The I will try bumping to 1.25" before I buy another pump. Thank you

 

[DCR]

Pay attention to the final return connections at the tank as well. These high velocity nozzles like Locline flares will kill your flow rate unless you have a lot of them.

 

[Nate77]

Return at the tank is just pvc elbows hung over the tank. No lockline

 

[Bob Lauson]

You should get the data for your pump - specifically a curve that shows the pump head on the y-axis and the pump flow on the x-axis. If you can't get this, you should a least be able to get the performance data on the pump in terms of max flow which is the flow with zero pressure drop/friction losses and the max head for the pump usually expressed in feet. This is the head the pump will produce typically at zero flow. Ignoring the friction and pipe size as a starting point, measure the feet/head you have for the pump. Divide the feet you have by the feet that that the pump is rated for. Multiply this be the pump's max flow and this will give you (roughly) the best possible output of your pump with no friction losses. I am probably making this sound a lot more complicated than it is.

 

[Nate77]

This is the only thing I can find as far as data

 

[Bob Lauson]

That's all you need to start. Assume you have the DCP-2500. With no plumbing attached the pump will produce 2000 L/Hr (528 gallons/hour). Pumping to a height of of 2.0 Meters (6.4 feet) the pump will have zero flow. Assuming that the distance from the pump outlet to the top of your display tank it 3 feet, the pump will produce: (6.4 feet- 3 feet)/6.4 feet x 528 Gallons/hr = 280.5 gallons/hour with no plumbing losses.

The next stop would be to look at the plumbing for friction losses. If you google PVC Pipe pressure losses you can find data on the equivalent loss (in feet) that you start adding to the 3 feet height that you are overcoming. A typical table you can find will look like the chart below for 3/4 in PVC pipe. You have a flow rate of 280.5 gallons/hr or 4.7 gallons/min. Just to make it simple assume your flow rate is 5 gal/min. Looking at the chart below, you would have a friction head of 5.7 ft/100 ft. So when you add up the length of all the piping to get to the top of the tank (ignoring valves and elbows for the time being) let say you have 4 feet of pipe. The additional head associated just with the plumbing would be 4 feet x 5.7 ft/100 ft = 0.2 feet. Add this to your height and you get 3 feet + 0.2 feet = 3.2 feet so you flow would now go down to (6.4-3.2)/6.4 x 280.5 gal/hr = 264 gal/hr or 4.4 gal/min. There are additional losses for fittings and valves but this will at least get you in the ball park. (To really do this right, you would have to iterate on the pressure drop a few times because now we are estimating your flow rate is a little less than what you first figured and you would go back to the table below and get a new friction head value. You will end up being somewhere between 5.0 gal/min and 4.4 gal/min)

I hope this helps at least giving you a starting point. When in doubt, oversize the pump and then you a tee fitting with a valve on the pump outlet and you can open the valve a little to dump excess flow back to your sump.

 

[Nate77]

Thank you Bob
So if my math is right following the info in your first paragraph.
19.69-4/19.69 = .79685 x 3646gph = 2905.3 gph or 48.42gpm
Which I can't find that number on a 3/4" pressure loss chart. But looking at charts I should be running at least 1 1/4".
So this tells me A. My math is wrong or be I should up size to 1.25 -2" ?

 

[Bob Lauson]

Thank you Bob
So if my math is right following the info in your first paragraph.
19.69-4/19.69 = .79685 x 3646gph = 2905.3 gph or 48.42gpm
Which I can't find that number on a 3/4" pressure loss chart. But looking at charts I should be running at least 1 1/4".
So this tells me A. My math is wrong or be I should up size to 1.25 -2" ?

Which pump do you have?

 

[Nate77]

Jebao DCP 13000

 

[Bob Lauson]

Your math looks right and that is a lot of flow to put through a 3/4" PVC pipe. The flow of 48.4 gpm is off the chart but pressure drop is approximately equivalent to the square of the flow rate so if the pressure drop is 72.3 ft/100ft at 20 gpm, the pressure drop at 48.4 gpm would be 423ft/100ft. So the pressure drop in your system would be somewhere around 4 x 423/100 = 16.9 ft. Your total pressure drop then becomes 4 ft + 16.9 ft = 20.9 ft which exceeds the capability of your pump without even accounting for valves and fittings You definitely need to either select a smaller pump or change the pipe size. For your reference, the pressure drop tables I have used are available at: https://www.engineeringtoolbox.com/pvc-pipes-friction-loss-d_802.html

 

[Nate77]

Thank you @Bob Lauson , that link is the tables I used. So a smaller pump or larger pipe will accomplish the same thing?

Ill have to do some math on the other pumps and see where it comes out.

Thank you so much

 

[Bob Lauson]

Yes a smaller pump or large pipe can be used to accomplish the same thing. However, running a large pump through a system with high pressure drop will mean your pump is running very inefficiently - you will be consuming more power than you need to. In fact running this type of pump with a really high pressure drop will mean that slight change in the pressure drop - a valve setting, an additional fitting, etc - can lead to larger changes in flow than you would expect. Without getting into too much detail, centrifugal pumps (like this one) do not operate very well when they are running either too high or too low on the head vs flow curve for the pump.

 

[Nate77]

Got ya dropped the pump back to 30% working it up from there see it makes a difference ,before I start fooling with plumping.

 

[Nate77]

So I dropped the pump to Run at 30% , and have been increasing in increments of 5 over the course of the day , can't seem to get overflow to quiet down still , seems like there is not enough water over the pipe in the outside box

 

[DCR]

I think you are misunderstanding the post. Lower flow rates are better suited to your existing piping, but there is no way you are going to get more flow by turning your pump down. Is the issue the noise from the overflow or low flow. If it is the noise, it may just be that your overflow set-up is not the best. Are you running a Herbie or Bean Animal?

 

[rockskimmerflow]

Full replumb in 1.5" piping; Fluval SP6

I don't see a way to make it work quietly or efficiently through 3/4" pipe. You'd need an iwaki 100rlt to sufficiently accomplish your goals with 3/4" lines. But then you'd be using 300 watts+ 24/7 to make it happen... with a loud pump to boot.