Lawn Sprinkler Chemical Injection

[John Williamson]

As a lockdown project I'm trying to complete a lawn sprinkler system I started last year (in the previous lockdown).

I have two sprinklers which are on timers to irrigate my lawn which work really well. My pressure at the tap is 46 PSI (approx. 3.17 bar).

I would like to be able to inject/mix chemicals (Liquid seaweed mainly) into the water supply so the mix comes directly out of the sprinklers.

Last year I tried with multiple different Venturi Fertiliser Injectors between the mains tap and the manifold but could not get them to work. Probably the pressure differential was not high enough.

Does anyone have any experience or clever ideas of solving this? I was thinking of a Peristaltic dosing pump which I have lying around but have no idea how to connect this to the main flow or even if this would work.

Any advice much appreciated.

Current kit list:
Rain Bird 1” 2 Way Manifold
Rain Bird 1" HV Solenoid Valve - 24V
Threaded Director 13mm x 1" BSPM
2 x RainBird 32SA

 

[WorthFlorida]

The problem is only two sprinkler heads. Venturi type you need a lot of flow to create low pressure to draw up a liquid. If 46 PSI is the static pressure it's kind of on the low side. City water supply in the USA is generally over 60 PSI and higher. A pump could work but be sure to place a check valve between the pump pipe. One issue will be to have a float switch to shut off the pump when you run out of the seaweed liquid. This was the first time I ever heard of liquid seaweed and I had to look it up. In the USA I never seen it and almost all fertilizers are granular. Other than maybe in agriculture, it is not recommended to apply any chemical in an aerosol fashion with a sprinkler system. Too much drift from winds where people can be contaminated and inhale it. However, seaweed no doubt is 100% natural. Liquid herbicides and insecticides are applied in spray form but it's regulated when used commercially requiring a certification. For the homeowner it's not.

The only time I've seen chemical injection, and it can still be found, was to mix an chemical that prohibited iron from oxidizing creating rust stains on everything. Shallow wells (~40 ft) in South Florida is loaded with iron. Before the 1980's most wells were shallow for irrigation. Now about 80 ft down you'll get sulfur water but no rust stains. However, it only worked on well pumps. You drilled a hole into the suction pipe, inserted a fitting with a built in check valve, ran a thin tube to the container.

 

[Sponsor]

 

[John Williamson]

The problem is only two sprinkler heads. Venturi type you need a lot of flow to create low pressure to draw up a liquid. If 46 PSI is the static pressure it's kind of on the low side. .....

Thanks so much for the response. One thing I should have said is that the sprinkler heads do not run simultaneously. The Solanoids switch on the first sprinkler for a time and then the other so both would get the 46 PSI if my maths is right.

You drilled a hole into the suction pipe, inserted a fitting with a built in check valve, ran a thin tube to the container.

This is kind of what I was thinking of for the Peristaltic dosing pump which has a 2mm inner Dia x 4mm outer Dia. but haven't been able to find any kind of connectors/valves which would work

 

[WorthFlorida]

Google "micro check valves" and "micro drip irrigation". I did find this USA site https://www.usplastic.com/catalog/item.aspx?itemid=32233. Micro drip irrigation uses tubing that is 0.245 in. O.D., 0.165 in. I.D. (4.191 mm). I'm assuming micro drip irrigation is the same in the UK. https://www.amazon.co.uk/Automatic-Drip-Irrigation-Kits/b?ie=UTF8&node=4224931031

https://store.rainbird.com/t22-50-1...f-IeRPCu8471VcHj4RQ-7Sd1sykPK0GoaAtEZEALw_wcB

From searching seaweed liquid, it only has a 0-0-1 as a fertilizer but I'm guessing that it is loaded with micro nutrients. In the US we have Milorganite organic fertilizer and I use it a few times a year. At the Amazon UK site in searched it and liquid seaweed pops up.

 

[John Williamson]

Google "micro check valves" and "micro drip irrigation". I did find this USA site https://www.usplastic.com/catalog/item.aspx?itemid=32233. Micro drip irrigation uses tubing that is 0.245 in. O.D., 0.165 in. I.D. (4.191 mm). I'm assuming micro drip irrigation is the same in the UK. https://www.amazon.co.uk/Automatic-Drip-Irrigation-Kits/b?ie=UTF8&node=4224931031

https://store.rainbird.com/t22-50-1-4-in-blank-tubing-50-ft.html?utm_source=google&utm_medium=cpc&utm_campaign=RainBirdPLA&utm_term={keyword}&gclid=Cj0KCQiA3Y-ABhCnARIsAKYDH7uUWd2uSP8dWhTXX7Nx9eNf-IeRPCu8471VcHj4RQ-7Sd1sykPK0GoaAtEZEALw_wcB

From searching seaweed liquid, it only has a 0-0-1 as a fertilizer but I'm guessing that it is loaded with micro nutrients. In the US we have Milorganite organic fertilizer and I use it a few times a year. At the Amazon UK site in searched it and liquid seaweed pops up.

Thanks so much. Yes I have some of those connectors but the bit which I can't get is how to get this tiny tube into the centre of a 1" BSP pipe without leaks.

I took a punt on buying this this morning. EZ-FLO 2005-HB 3/4 Gallon Low Pressure Hose Bib and Drip Connection Fertilizer Injector System.
https://ezfloinjection.com/products/dis ... oggle-id-1

Has a max of 50 PSI so should be great for my needs. So I'll put a solenoid before this in the system (as it shouldn't be permanently under pressure) followed by the manifold to the two sprinklers. Fingers crossed. I'm kind of expecting it to go the same way as the Venturi's and not be able to suck up the liquid but we'll see.

 

[Reach4]

In the US we have Milorganite organic fertilizer

I expect that has lots of micro constitutions. People put some bad things down toilets and drains that are not body waste.