Question on Pump Strength and pipe size

[texmaster]

So I'm redoing the pipe from my bottom drain to the pump. The bottom drain is 3.5 feet down and its about 5 feet to the edge of the pond. Right now its reduced to 1.5 which is obviously too low. The pump is about 20 feet away. Right now my plan is to bring the 4inch pipe to the surface so another 3.5 feet directly up then once on the surface after a check valve only reduce it to 3 inches for maximum flow until the basket then reduce again to 2 inches which is what the pump is rated for.

This is the basket I'm considering

http://www.calponds.com/Evolution-Pu...ap-p-6719.html

My question is can this pump handle a 4 inch 9 foot piple + 20 foot 3 inch pipe and still maintain decent flow?

Here are the pump stats.

• Inlet & outlet: 2 inch MPT. Two 2 inch FPT unions are included.
• Max Flow: 5800 gph
• Max head: 21 ft.
• Max Watts: 296
• Max Amps: 2.6
• Horse Power: 1/4
• Comes with an 8 ft. 115 volt power cord.
• Material: 40% Glass - Filled Polypropylene
• Hardware: Stainless Steel
• 3 year limited warranty
• Manufacturer Model Number: 5800SEQ22
• Made in USA
• Installation and Service Manual (1MB PDF file will open in a new tab or browser window)

Comparison Flow Rates for Sequence 4000 Series Pumps
Model No. 5800SEQ21
GPH @ 4 ft 5520
GPH @ 8 ft 4500
GPH @ 12 ft 3720
GPH @ 16 ft 2760
GPH @ 20 ft 690

 

[mgmine]

No. A 4" pipe would be a drain pipe. There is no reason to go larger than 2".

 

[texmaster]

No. A 4" pipe would be a drain pipe. There is no reason to go larger than 2".

Should I at least bring the 4 inch pipe to ground level so if there is a clog its easier to get to?

 

[addy1]

The four inch line could be used then the three like you are saying. It would make an easy draw for the pump. I have three inch decreasing to 2 inch right at the pump. Around 10 - 15 feet or so.

 

[texmaster]

The four inch line could be used then the three like you are saying. It would make an easy draw for the pump. I have three inch decreasing to 2 inch right at the pump. Around 10 - 15 feet or so.

Where should the 3 inch begin vs the 4 inch? This is NOT a dirty discussion!

 

[addy1]

Totally up to you. Or just run 4 to the pump. The two into the pump will be the limiter, but the four gives it a wide open flow to that point. There are charts out there about head pressure and pipe size, the return decreases at x point but I do not recall the x.

 

[mgmine]

The pump is rated at 5800 gph. That flow will not be increased by using a larger pipe. The only thing that a larger pipe would do would be to reduce friction. The distance that you are talking about is so short that I doubt that you will notice anything. If you are having a problem with the pump then it would be because you are pulling the water 20 feet instead of pushing it.

 

[crsublette]

3 inch would definitely make friction loss very negligible.

I bet you would still be pumping near 5,000gph... although may significantly change dependent on type of check valve you are using, any other valves, and pipe adapters.

Would not surprise me if your pump documents didn't recommend 3".

@texmaster , if you really want to understand this flowrate and friction stuff... I recommend you studying the first 2 references below

http://www.google.com/url?sa=t&source=web&cd=1&ved=0ahUKEwi7pd2_l4bOAhWs7oMKHecYATMQFggcMAA&url=http://www.koiphen.com/members/harveythekoi/plumbing.pdf&usg=AFQjCNHWbcBfUvlrlhjmTiCFbG-N86liPg

http://www.mcnallyinstitute.com/07-html/7-01.html

And... once ya understand that.... check out...

http://www.engineeringtoolbox.com/npsh-net-positive-suction-head-d_634.html

I bet the 20 horizontal feet on the suction end will have minimum impact, depending on... again... type of check valve, and other pipe adapters and elevation of the suction portal above the pond water level... that might be involved in that 20 feet..

Swing... rather than spring... are the best low friction check valves... if you're curious... some of them may require further modifications to further reduce resistance...

 

[Meyer Jordan]

If you are having a problem with the pump then it would be because you are pulling the water 20 feet instead of pushing it.

Quite true.

 

[crsublette]

Pumps operate according to pressure displacement...

....Pumps do NOT "push" nor "pull" water..


The only coefficient that might be different between a pump "pushing" or "pulling" water is how the pump's impeller and suction flange are situated. With the pumps we use in this hobby, I have not seen this to be a concern.

To see this in mathematical quantification, read the 2nd and 3rd hyperlink reference in my previous post.

 

[Meyer Jordan]

....Pumps do NOT "push" nor "pull" water..

Need to explain the "do NOt push" part.

 

[crsublette]

@texmaster , if your check valve is spring or tension operated, then do not place it on your pump's suction side... cause these have a tendency to sometimes not open at all... and if that happens on your pump's suction suction side... then bad news bears...

Use a swing check valve if ya need a check valve on your pump's suction side... These valves simply use the weight of the water to close the valve. When the pump turns on, then this water weight is removed and the swing opens...


Here are two examples of them....

http://www.marinedepot.com/ps_viewi...ntent=FT9077&gclid=CNnqv4Loh84CFQyNaQodzCUCkA

http://www.usplastic.com/catalog/item.aspx?itemid=82995



Cavitation only occurs when liquid and vapor pressure coincide, according to water temperature... In a pond context, much tougher to cause a pump to cavitate than people realize... You would have to have some serious blockage or a valve at the suction side to cause this. This is why folks NEVER place a valve on the suction side of a pump.

A good way to know if cavitation is occurring with the pump is to... install a compound pressure gauge (that is a psi gauge showing both vacuum and positive psi)... find out the Vapor Pressure variable for your water temperature, subtract this from this compound pressure gauge read... then... reference your pump's Net Positive Suction Head capability, as determined by the manufacturer... the compound pressure reading minus vapor pressure cannot be lower than the pump's suction capability... if it is, then cavitation will occur and will ruin your pump.

 

[crsublette]

Need to explain the "do NOt push" part.

@Meyer Jordan , wiki does a better job at answering this than I do... I think I mangled it a bit.


There are pumps made specifically for pushing (positive displacement pumps) or pulling (vacuum pumps), but our typical centrifugal pond water pumps are neither of these..

Centrifugal (radial flow) pumps uses the rotational energy to create a pressure displacement and this is what moves the water.

https://en.wikipedia.org/wiki/Pump#Positive_displacement_pumps

https://en.wikipedia.org/wiki/Centrifugal_pump

...so... technically.... the centrifugal water pumps used in our hobby do not push nor pull... they simply create pressure to move the water...

Cavitation can definitely occur if the water temperature is higher and suction friction head is too low (or high depending on how ya look at it)... but the suction friction head allowance can be much higher than people think...


The Zakki Sieve (http://www.deepwaterkoi.com/Zakki-Sieve-The-Direct-Suction-Pre-Filter-Zakki-Sieve.htm)...

...is driven by pump suction and there is notable friction head created by this filter...

...and I have seen people place this filter up to 50 feet away from the pond.

...and no notable risk to pump nor any significant flow rate reduction.... just the same as would be expected if on the pump discharge.

 

[crsublette]

The reason why centrifugal pump's flow rate slow down as friction increases is due to the water weight pressure on the blades...

...depending on the pump... more pressure (or restriction/weight/whatever) on the pump then this forces the pump's motor to slow down and a decrease in electricity...

...however, water helps to keep the motor cool... so, if water restriction on the discharge is too high, preventing enough water to pass by the motor, then this will cause the motor to overheat and "burn up"...

There are always wattage fluctations in centrifugal water pumps as pressure changes, either due to water temperature changes or flow resistance changes.

Centrifugal pumps are all about pressure displacement.

 

[crsublette]

@texmaster , here is a friction loss chart to show you the difference between a 2 inch, 3 inch, and a 4 inch pipe at a water flow of 5400gph.

http://www.engineeringtoolbox.com/pvc-pipes-friction-loss-d_802.html ... this is "per 100 feet" ... so just divide the coefficient value by 10 to get "per 10 feet".

...that is HORIZONTAL feet....

2 inch @ 5400 gph - 1.24 friction head per 10 horizontal feet
3 inch @ 5400 gph - 0.18 friction head per 10 horizontal feet
4 inch @ 5400 gph - 0.05 friction head per 10 horizontal feet

So the difference between 2 and 3 inch on friction loss for 5400gph is HUGE .... 4 inch a little less so...

I wouldn't go 4 inch because 4 inch adapters are quite expensive.


....Generally, if you have any vertical feet... then this would be equal to friction head... 1 vertical foot = 1 friction head... not always true, but good enough for our context.