Poor Flowrates.

[Naplumb]

Hi everyone.
I am sure this has been discussed before but I have a query about a Jet pump installation.
I have a problem with poor flowrates into my newly purchased property. The kitchen sink has 11L/min.
The installers fitted 260 feet of 32mm mdpe plastic piping on a horizontal run to the suction side of the pump which draws its water from a dug well 21 feet deep.
The pump is a Dab Jet 62M.
Have the installers got it wrong ?.
Any help appreciated.

 

[BigInch]

A quick look at the hydraulic data for the 62M,

http://www.colglo.co.uk/products/files/JET_Technical.pdf

gives a discharge head of round 32m. The head loss in the pipe appears to be less than 4 ft.

I don't see the suction lift data for the pump. A 21 ft lift may be too high.

http://virtualpipeline.spaces.msn.com

 

[Naplumb]

Thanks for the swift reply.
This link gives some more explanation.

http://www.goulds.com/pdf/bpump.pdf

I have my own views about the system but just wanted to hear a few others.
Many thanks.

 

[Artisi]

A better explanation of what you see the problem is would be helpful.

Does the unit pump to a pressure tank - or is it connected directly to the tap?

The kitchen sink has 11l/m - what does this mean- you are only able to deliver 11l/m at the tap or is the tap flow restricted to 11l/m ?

 

[Naplumb]

Basically their is a poor flowrate into the property.
The kitchen sink is not restricted albeit through pipe resistance though 1" copper pipe is fitted to the discharge side of the pump.
When another tap is opened and two running concurrently the flow rate reduces to a dribble.

The suction pipe concerns me.
Page 8 and 9 of the link I gave above gives information relating to Jet pumps and states clearly that they deliver inadequate capacity on lifts over 25ft.

Surely the resistance on 260ft of blue MDPE 32mm piping with an internal bore of 25mm will give a much higher head loss of 4ft.
I think 100ft will give close to 4 ft alone (including fittings and elbows) and add this to the 21 ft and we have crossed the threshold of 25 ft hence the problems.

Have the installers got it wrong ??.
Many thanks.

 

[BigInch]

Actually its much less than 4 ft. More like 1.4 (typo) You don't have enough flow to get any high head loss.

I still think its the lift height.

If you want to check, disconnect (or open a side tap) at the pipe at the pump discharge and test the flow there.

http://virtualpipeline.spaces.msn.com

 

[Naplumb]

Thanks for the reply Biginch.

 

[Artisi]

One obvious question not yet asked, is the well capable of being pumped at 11 l/m . It is possible that you are pumping the well down to a low level and exposing the inlet pipe and entraining air into the system.

What is the pumping level in the well-- what is the discharge side configuration - how much pipe what length and what is the difference in elevation from the well draw-down level to the discharge point - your tap.

Regarding friction losses:-

Is the suction pipe actually 1"ÏD. As I don't have a friction chart for 32mm plastic pipe I have assumed that the ID is 1" as advised and have used a 1"copper pipe as a model for the friction loss. Therefore, 1" ID copper pipe has a Hfl of 0.92 ft / 100 ft @ 3USGPM (11 l/m), this equates to approx 2.4 ft head loss - let's say 3ft total to allow for bends etc.

Once we know the pumping level in the well and the discharge pipe work and elevation we can assume the pump total head.

Re the total head on the inlet side - again we don't know the draw-down level in the well but lets assume it is less than 21 ft - lets say 19ft + the friction loss of 3 ft which gives a total of 22ft - according to the curve posted by BigInch you pump is capable of pumping round 11l/m at a lift of 9 metres.

Like BigInch I would guess that the problem is on the inlet side, however, as stated above - pumping to a level that allows air into the inlet - or a blocked inlet pipe, or the well not capable of giving 11l/m

 

[pumpguykc]

JUST TO BE SAFE YOU MAY WANT TO SEE IF THE PUMP IS RUNNING BACKWARDS. IF THE PUMP RUNS BACKWARDS YOU WILL STILL GET SOME FLOW RATE BUT IT WILL BE LOW. IT MAY BE WIRED WRONG. I WOULD HAVE YOUR INSTALLER CHECK YOUR ROTATION AS AN OPTION AS WELL.