Comment by mmmBacon | Hacker News Reader

Comment by mmmBacon | Hacker News Reader

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So one issue with what you posted is that it's a recipe for contaminating your drinking water. You need to have some type of anti-siphon device to prevent the back flow of water from your irrigation system into the house water supply. My guess is that somewhere the farm you are talking about had a giant and very expensive double check back flow preventor. Having designed and installed several irrigation systems I can tell you that pressure drop is a thing. To get the correct CFM, I had to install 1 1/2" mains so that the rear of my lot would have enough pressure to deliver the cfm I needed. Also, water hammer is a thing if you have lots of pressure. Your consumer grade fixtures will be destroyed by water hammer and your system will need lots of maintenance. Also, if you live around the system, water hammer is noisy and when your system trips on at 5am, it's going to wake you up. So while I don't doubt the farm did this, I'm not sure it's an appropriate installation for a home owner that just wants the system to work reliably for years with little to no maintenance.

Your water hammer reference reminded me of a setup I once saw. It used a hydraulic ram to get water from a small waterfall (maybe 5m fall) up to a stock trough about 50m up and 200m horizontal. Those rams are awesome - and loud.

Did you have a way to release excess air from the hydraulic ram? I set one up with similar dimensions to what you described but it would always quit after about 15-30 minutes, presumably due to air in the line. If I evacuated the line and got it going again then it would run for 15-30 mins again and then stop. Never figured out a solution :(

It wasn't a homebrew solution and came as a kit. I'll try and find out where it was from. Presumably it had a way of releasing the air as it would go fine for weeks (until a flood took it out). The thing was awesome and could have gone way higher (with reduced flow). It had so much water running into the trough that the main issue was trying to work out how to reduce the flow, which is surprisingly hard.

In California every outdoor spigot has to have an anti-siphons installed directly on it, so it’s not too hard to imagine that being the case here.

And they adjusted for low water pressure by poking a few more holes for each plant nearer the end of the the poly tube. By avoiding "nozzles" on their tubing - which would require pressure to operate -- they greatly simplified the design of their irrigation system.

Wouldn't you have to replace sections of tube each season with this approach?

That's true - I asked about that and they said that they could sometimes reuse the tube if they were planting in a similar configuration - otherwise they just discarded the tubing (it is very cheap - another advantage of their system.)

Again anything that moves liquid from point A to point B requires water pressure or the liquid will not move. So the system you describe still requires water pressure to operate. I really don't see how this simplifies because you have to empirically determine the number of holes at each plant. If you have thousands of plants, I just don't see how this is efficient or scales. Maybe I'm missing something. For small numbers of plants maybe it can make sense. Driving through Watsonville, Ca today on my way home from the beach I saw hundreds of rows of crops growing with traditional drip lines.

Go visit the UCSC agroecology center farm. They have been using variations of this technique for years. I was surprised when I saw it too - I'd thought that it would need to be more complicated.

I've owned several houses in California and not one has had an anti siphon valve on it. A quick check around my neighborhood shows that non of my neighbors do either (at least on their front yard spigots).

I wanted to run a tap with flow backwards and found that all outside taps in both big box hardware stores near me had a valve in them. There was no way to tell this externally.

Sorry but this is not correct. The anti-siphon valve is almost always apparent. These spigot valves are not very good and fail pretty regularly so I would not trust my drinking water to them.

Also an anti-siphon valve only works if it's above the water lines. If you store a hose above the spigot like many people do, you've just defeated the valve.

Every outside tap here in New Zealand is required to have a back flow preventer (is this a different thing?). They all passed the recent test they had which was required by the local council and they are all pretty old. The 'check valve' is required to be replaced every two years as it can't be tested according to the documentation here. I don't known what this is and don't have one.

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