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Poor Flowrates.

Poor Flowrates.

Poor Flowrates.

(OP)
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.

RE: Poor Flowrates.

(OP)
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.

RE: Poor Flowrates.

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 ?
  

RE: Poor Flowrates.

(OP)
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.








RE: Poor Flowrates.

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

RE: Poor Flowrates.

(OP)
Thanks for the reply  Biginch.

RE: Poor Flowrates.

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  

RE: Poor Flowrates.

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.

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