Agri Vehicles Insurance from Greenlands

Author Topic: 12v pump for irrigation  (Read 190 times)

GribinIsaf

  • Joined Aug 2015
  • Montgomeryshire
    • Gribin Isaf
12v pump for irrigation
« on: November 20, 2020, 04:20:30 pm »
I am experimenting with some sprinkler irrigation in a polytunnel.  I got a few standard dropdown spinklers fully expecting not to have the pressure to drive them - and that proved to be true.

The seller of the sprinklers says they need 2 bar to operate.  I tried them with an IBC store which is about 3m above the polytunnel and also the water tank in in our loft which is fed by a bore hole and maybe about 4m above the polytunnel.  The pressure from both sources is also of course decreased by the friction in the pipework.

I have got a tank sunk into the ground in the polytunnel so about 2.5 lift with minimum pipework from there.  I would like to use a 12v pump - maybe a bilge pump or waterfall pump? - got to be able to handle non-pure water, to lift from here into the sprinklers.  I have tried a couple I have lying around but they don't produce enough pressure.

Pumps seem to be rated in litres per minute or similar.  How to a calculate the pump I need to lift water and deliver at 2 bar?

cloddopper - if you see this I bet you will know

Thanks.




arobwk

  • Joined Nov 2015
  • Kernow. Some like to think it's in England.
Re: 12v pump for irrigation
« Reply #1 on: November 20, 2020, 05:33:49 pm »
I would also be interested in any recommends for 12v water pumps.

mab

  • Joined Mar 2009
  • carmarthenshire
Re: 12v pump for irrigation
« Reply #2 on: November 20, 2020, 06:08:37 pm »

I can't really advise on which pump to get, but 2bar is about 20meters/70feet vertical height ('head'). I suspect it may be more practical to find a watering system that works at lower pressure - particularly if you're not using mains or filtered water as any debris will clog the holes in a high pressure spray system.


some pumps spec sheet will include a chart of flow vs head, or at least a value of flow rate at a given head. If they only give you max flow rate (at zero head) and max head (at zero flow) I'd probably look elsewhere.

chrismahon

  • Joined Dec 2011
  • Gascony, France
Re: 12v pump for irrigation
« Reply #3 on: November 20, 2020, 07:27:42 pm »
Pumps are rated at a delivery with zero head. To get a delivery at an increased head you need to look at the manufacturers charts. 2 bar is 30 metres head and I think it unlikely any 12V pump will deliver that.
To give you an example we have a 750W mains vortex pump (handles solids to 30mm diameter) rated at 4.5 litres per second, so a gallon, but at 9 metres head it reaches its limit and delivers nothing.


As Mab says, look at an alternative system.

oor wullie

  • Joined Jun 2012
  • Strathnairn
Re: 12v pump for irrigation
« Reply #4 on: November 20, 2020, 07:40:54 pm »
You will need;
2 bar (pressure loss through sprinklers)
+
0.25 bar (to overcome 2.5m hydrostatic from your tank to the max height og the system (make sure you are measuring from the bottom of the IBC))
+
Pressure loss through the pipework.  If its a short distance through large ish pipe (eg 32mm) it's probably insignificant. But, small diameter pipes (in particular) and long distances can make it significant.

Your individual sprinkler might work on 2 bar but remember if you fit them in series along a pipe the pressure will have dropped by the time the water gets to the downstream ones.

My polytunnel sprinkler system needs about 3 bar to work well but that's after I've lost 2 bar in the pipework (water is piped about 450m to get to the tunnel) so I need a water supply at about 5 bar.


For a blind guess, look for a 4bar pump.

GribinIsaf

  • Joined Aug 2015
  • Montgomeryshire
    • Gribin Isaf
Re: 12v pump for irrigation
« Reply #5 on: November 20, 2020, 07:51:21 pm »

I suspect it may be more practical to find a watering system that works at lower pressure - particularly if you're not using mains or filtered water as any debris will clog the holes in a high pressure spray system.


yes, I thought this might be a route to take - anyone got any links?

 

Gravity fed irrigation - any thoughts?

Started by arobwk

Replies: 30
Views: 5978
Last post August 02, 2018, 08:35:41 pm
by arobwk
A Simple Solar Powered Garden Pump

Started by Carolinajim

Replies: 5
Views: 3403
Last post July 25, 2009, 11:24:44 pm
by sausagesandcash
Help needed to fix well/spring pump Nr Cardigan, Wales

Started by Shinding

Replies: 4
Views: 1913
Last post September 08, 2016, 03:33:10 pm
by bazzais
MOVED: Ground source heat pump - advice needed please

Started by Dan

Replies: 0
Views: 1517
Last post September 14, 2011, 08:20:34 am
by Dan

Forum sponsors

FibreHut Energy Helpline Thomson & Morgan Time for Paws Scottish Smallholder & Grower Festival Ark Farm Livestock Movement Service

© The Accidental Smallholder Ltd 2003-2020. All rights reserved.

Design by Furness Internet

Site developed by Champion IS