Browse Forums Landscape & Garden Design 1 Oct 07, 2013 12:01 pm I've just installed my first drip irrigation system across 4 raised vegetable beds. This is what my (simplified) setup looks like: Tap | Tap timer | 100 kPa pressure reducer | Filter | | | 12m of buried 13mm tube | | -------- Garden bed 1 (10 x veriflow 0-60Lph tricklers) | | -------- Garden bed 2 (10 x veriflow 0-60Lph tricklers) | | -------- Garden bed 3 (10 x veriflow 0-60Lph tricklers) | | -------- Garden bed 4 (10 x veriflow 0-60Lph tricklers) Each bed has an inline 13mm valve. I have found that if I run each bed individually, then I get good flow and coverage from each trickler. If I turn on the valve for all the beds at the same time, I only get a dribble out of each trickler. I tried replacing the 100 kPa pressure reducer with a 300 kPa reducer, but that didn't seem to make any difference. I called Pope and they said that my only option is to run a line to each bed and buy a multichannel tap timer. They said that replacing the 13mm main line with a 19mm or 25mm main line won't make a difference. Is it true that using 19mm/25mm tube for the main line won't improve the flow at each emitter? Thanks Re: Drip irrigation - lack of flow 2Oct 07, 2013 3:52 pm rsmith32 They said that replacing the 13mm main line with a 19mm or 25mm main line won't make a difference. I will keep this as simple as possible. A standard 15 metre 12 mm garden hose will flow at about 16-18 litres per minute (lpm) when supplied by mains water pressure. To double the flow rate requires about 4 times the head pressure. Going from 100 kPa to 300 kPa won't give you the increased flow that you were probably expecting. The filter adds to the already reduced loss as do the (40) drippers. You would normally design the irrigation system around the dynamic head/flow rate. If let's say your expected flow rate was 5 lpm, this equates to .125 lpm or 7.5 litres per hour (lph) per dripper. 1. A 13 mm poly pipe loses about 0.4 kPa per metre at 5 lpm. While changing to a 19 mm poly pipe for the main line will reduce this friction loss to about 0.07 kPa per metre, the additional flow rate would be minor. It must also be understood that the pressure in the main feed line further reduces after each branch in any case. 2. The most efficient soil hydraulic conductivity is recognised as between 2 and 4 litres per hour. This is why gravity fed drip hoses are designed with (twin) emitters that drip at 2 lph. To achieve this optimum flow through your drippers, your garden tap needs to only deliver 2.5 lpm. NOTE: Gravity fed drip hoses are much different to the drip hoses that people use on garden taps. They operate with very low pressure (usually from rainwater tanks) and the emitters are larger. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Drip irrigation - lack of flow 3Oct 07, 2013 3:59 pm Thanks. So my options are: 1. Install additional main lines and a multichannel tap timer 2. Run an emitter to the base of each plant so that coverage doesn't matter. Run the tap timer for longer to compensate for the lower flow. Correct? Re: Drip irrigation - lack of flow 4Oct 07, 2013 4:08 pm The coverage radiates due to capillary effect. As a guide, the quality gravity fed drip hoses have emitters 300 mm apart. I would measure the hourly flow through several drippers to see what the flow rate is and then set the timer accordingly. It is best to use a 19 mm poly main line but I wouldn't go to the trouble of changing your current set up for the situation as described. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Hi All! I have engaged a plumber to re-do the stormwater drainage system on my property which is mid-70s and had blocked/cracked clay pipe drains. The works has… 0 18708 Good luck with it. I don't know what the cost of a nice bidet seat with a 25mm air gap will be but you are obviously deducting the cost of a RPZ valve and its… 9 6983 You may still have a case, but your next step is to speak to a lawyer. 3 1624 |