Sump pump discharge sizing

[amcclur]

Hello,
I’m looking for a little advice on if I should upsize the discharge on my home’s sump pump. After upgrading the pump size it still can’t keep up, but only by the smallest of margins during absurd amount of rainfall. I’m making other improvements to prevent water making it to the sump pit but was wondering if upsizing the discharge line, which is an easy fix, would help in the meantime. The current setup is as follows:
Pump:
Flotec ½ HP
0 head = 4680 GPH
5 head = 4380 GPH
10 head = 3840 GPH
15 head = 3300GPH
20 head = 2340 GPH

Discharge:
1 ½” PVC
10’ vertical run
Single smooth 90 degree elbow
23’ horizontal run
20’ of 1 ½” corrugated discharge line

What is the maximum discharge of the current setup and would upsizing to 2’ improve the output?

Any help you may provide would be most appreciated. Thank you.

 

[bimr]

You might be able to get an additional 600 GPH if you upsize the line from 1.5-Inch to 2-Inch. (assuming rigid pipe).

What is really hurting you is the corrugated discharge line. Corrugated tubing has very bad hydraulic properties and much higher resistance to flow.

It is not clear from your post where the 20' of 1 ½" corrugated discharge line is installed. So it is difficult to estimate the flow increase.

In any case, I would replace the 20' of 1.5" corrugated discharge tubing with pipe.

 

[amcclur]

Thank you for the reply.

The solid PVC run includes the vertical to the basement ceiling and out to exterior wall, where it is connected to the 20' of 1 1/2" corrugated line on the exterior.

 

[chicopee]

Corrugated piping has at least twice the friction loss of smooth pipe. Assuming your piping is running full of water when the pump is energyzed, it appears that you are well outside the useful parameters of your pump.

 

[cvg]

For 1 1/2 inch line you are running about 7 - 8 fps. Drop your velocity to 3 or 4 fps and you can really reduce the friction loss in the pipe and fittings. you could go up to 2 1/2 inch and maximize your pump output. I wouldn't go any larger than that.

 

[DubMac]

If I'm reading your data correctly, you will never get MORE than 3840 gph out of your pump because it takes 10' to satisy the static or lift portion of your discharge head.

You can look in a piping handbook to get the friction losses in your system now for various flows. Usually these losses will be in psi/100'ft. Of course 1psi=2.31 feet head.

Just look at the difference in losses between 1-1/2" pipe and any larger size you want to install and make sure the difference is going to be worth the changeout. I am too tired right now to go over how to convert the deltaPs into flow changes.

 

[amcclur]

Thank you all for your input.

I concede I'm starting with 10' of head (3840 gph max), however would replacing the 1 1/2" PVC with 2 1/2" reduce the the friction loss significantly? I imagine I'm close to a 20' of head loss with the current setup, if not more.

Not including the 20' of corrugated hose what would be the max output for my current setup? What would it be with 2 1/2" PVC?

How large of an effect would replacing the corrugated with PVC have?

Thank you for your help.

 

[BigInch]

If you tell us the flowrate you're getting now, we could tell you how much you can improve it. Otherwise the only thing we can say is that 3840 is an absolute maximum without any pipe loss included. From what you are saying, the present head loss is around 30 ft, and from what you ARE NOT saying, quessing a present flowrate of perhaps around 1500 gph, you may be able to as much as double that flow.

From "BigInch's Extremely simple theory of everything."

 

[bimr]

Here is a link for an online headloss calculator.

http://www.irrigationtutorials.com/faq/psi-loss-calculator.htm

Assuming the corrugated pipe is removed, use the calculator to estmate the pipe losses due to flow:

@3840 gph 1.5-Inch pipe headloss = 6.4 Ft

@3840 gph 2-Inch pipe headloss = 1.9 Ft

@3300 gph 1.5 -Inch pipe headloss = 4.9 Ft

So you are probably pumping approximately 3100-3200 gph (without the corrugated piece). If you replace with 2-Inch pipe, you can probably get 3400-3500 gph. If you go with 2.5-Inch pipe, you can probably get 3800 gph.

 

[amcclur]

Thank you all for your help.

I came across this site:

http://www.engineeringtoolbox.com/pressure-loss-plastic-pipes-d_404.html

Assuming a flow rate of 3600 gph would the head loss for the 20' of 1 1/2" corrugated section be ~8 feet?

 

[bimr]

Don't see a Hazen Williams factor for corrugated plastic. If you use the Hazen Williams factor for corrugated steel, the head loss for the 20' of 1 1/2-Inch corrugated section equates to 29.3 feet.

http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html

I believe that you are using a factor of 120 which is for smooth wall plastic pipe and not appropriate for corrugated pipe.