Sunday, March 15, 2009

Automatic Watering of SIPs, Part 2

Prompted by a comment from Publius, I decided to follow up on my first post from last summer. Fair enough: I did call it Automatic Watering of SIPs, Part 1, which at least suggests I had more to say on the subject.

Problem is I'm not sure what to write. When I put up Part 1, I thought that I'd follow it with a list of all the "tricks" that I'd discovered along the way. There really aren't that many.

I talked a little bit about this in my response to Kathy last summer. Purging the lines of air bubbles is the hard part.



Here's how I do it.

First, fill the main reservoir--the yellow bucket in the picture-- high enough to let you gently push the connection between the hose and the siphon/supply line below the water level in the reservoir. In practical terms this means 3/4 full. Next, fill up all the SIP reservoirs, one at a time, with a hose. Now, if you attach a hose to the beginning--where the Hudson valve is suspended--of the one of the black siphon lines , open the other end of the siphon/supply line, and turn the hose on, you'll force out all the air with water. Once a full stream of water is coming out the end of the open siphon tube/supply line, abruptly close the open end of the line. Then, making sure that water is coming out of the end of each 1/4" whip, put each of the 1/4" lines into its respective SIP fill tube.

Lower the hose/siphon supply tube connection below the surface of the reservoir. Slowly unscrew the hose from the supply line, being careful not to let the hose kink, while the water is still running through the hose.

Now that all the individual reservoirs are linked via siphon tubes, you only need to control the height of the water in the main reservoir. Figure out the right height for your Hudson valve and you're done.


Last year I used a 5 gallon bucket as my reservoir. It has a relatively small surface area, making it hard to submerge the hose/siphon tube connection below the water level in the bucket without kinking the hose. I found out that this causes the water to stop, briefly, and introduces air bubbles. Not what you want.

To make it easier, this year I'm going to use a longer, flatter reservoir. Probably a 14 gallon Rubbermaid tote. This will let me lower the connection between the siphon tube and the hose below the waterline without any hose kinks/air bubbles.

Whenever the system isn't primed, it stops. You'll see the plants droop, and you know it's time to flush it out and get rid of air bubbles. That happened about once a month last summer and I'm not sure why it did. It might be the fill tube that goes down into each SIP is moving around too much. Or the 1/4" whip that goes into each tube gets pushed/bumped and no longer sits in the water reservoir . As a safeguard I'm trying to figure out a way to be able to see the level of water in each tub. I might put a clear vertical cylinder in the middle of each siphon line, mimicking another sip in the loop. That way I could quickly tell if it's gone off.

Any ideas on what else I could do?

There are (at least) a couple of limits to what I'm doing. The first is that the SIPs need to be on roughly the same level. In my case, since my individual SIPs have reservoirs 5" tall, that's the maximum height that can separate the highest and lowest SIP--on my slightly sloped roof--being regulated by one Hudson valve. The second thing is about the priming process. It determines how you lay out your piping system.

I found that you need to restrict the number of SIPs on each siphon line to a maximum of 12. The reason for this is that at some point there's not enough water coming out of the hose to fill the 1/2" main line and all the 1/4" whips that go to each SIP at the same time. And that's the only way to get rid of all the air bubbles: fill the entire section of siphon tube with water. Basic math can help here. The total cross sectional area of all the whips can't be greater than the cross sectional area of the 1/2" main line. Due to frictional losses, the area of the whips should be less. How much I don't know. Trial and error or a clever engineer could give the answer.

All this is by way of explaining why there are three black 1/2" polyethylene lines coming out of the yellow bucket in the photo above. Each of those lines runs in a loop around 10 SIPs. Since I have 30 planters on my roof, I have 3 main supply/siphon lines.

Guess I did have something to say.

Thanks Publius.

10 comments:

Publius said...

Thanks Bruce!

Jay said...

Excellent post! I really enjoyed reading it. I will be back for more!
Sincerely,
Jay
http://vgtrailers.blogspot.com/

dfansl said...

Hey bruce -
I set up your system as we discussed last year and had a similar problem with the system eventually failing due to air bubbles. I sealed around the plugs for the whips with a food-grade silicone sealant and that seemed to do the trick. Not 100% sure yet, since I didnt get around to it until September. But looked to me it was on the right track.

Bruce said...

dfansl, nice idea. I might give that a shot this year.

and J-

Noticed that one of your blogs is devoted to The Special One. Love the Show, haven't missed an episode.

"Be Champions!"

Jay Buster said...

This sounds like a brilliant system. This a.m. I ordered my Hudson Valve (only $20 from QC Supply! http://www.qcsupply.com ) and I'm walking out the door to buy the 1/4" and 1/2" irrigation tubing.

Would you please help clarify some details of the system for someone who needs an instruction manual to replace a light bulb?

Question 1:
re: "...connection between the siphon tube and the hose..."

My understanding:
The "siphon tube" is the black 1/2" irrigation tubing.
The "hose" is the white hose shown in the picture (made for RV drinking water but basically a garden hose).

How do you form the all important connection between the two?


Question 2:
re: "...open the other end of the siphon/supply line, and turn the hose on..."

Do you mean open and then later close the end of the 1/2" line (the line to which the 1/4" lines are attached) once water is flowing out of the now open 1/2" end?
If so, I would need a 1/2" plug that I can easily remove and insert...right?


Question 3:
Could you eliminate the 1" fill tube?

Step 1: Drill an extra "overflow hole" in the bucket.
Step 2: Insert the 1/4" supply line through this hole directly into the rez at the bottom of the bucket?

Thanks in advance!

Jay
Boulder, Colorado

PS - Couldn't sleep last night thinking about the design of the 2-bucket systems.

Bruce said...

Good questions Jay.

I'll try to answer them.

#1 - You've got the terms correct. You can get a "female hose thread to 1/2" tubing" connector where you buy the rest of the irrigation supplies.

#2 - Right. You open and later close the end opposite of your supply. If you fold the end of the pipe over on itself, you can use the 'crimp' that is made for this purpose--again sold as an accessory. It's just two attached rings of plastic that, by passing the pipe through, and back again, keep the crimp in place. You can do this repeatedly according to the mfg without breaking the plastic.

#3 - I don't see why not. I had mine in place and it's always nice to have a backup plan that let's me fill them manually with a hose if the whole thing failed to work. But it's working so far.

I bought my "Mister Landscaper" parts from Lowe's (free delivery if you order more that $50 btw). Here's a link describing some of the fittings.

johnk43 said...

Help! I can't get my hudson valve to work. What is the minimum amount of pressure needed? I am trying to run mine off the rain barrel, but I am getting the impression that that will never work.

Bruce said...

Hi Jk43,

I think you're right, the Hudson valve is designed to work off of a minimum water pressure.

This is from their troubleshooting page:

• There isn’t enough water flow coming to the valve. Your water source must be turned on full volume. We recommend having at least 8 lbs of pressure.

There must be a similar valve out there that you can use with rain barrels/low pressure systems. I haven't looked, but if you find one let us know!

Seffliva said...

Cool! I never try to use automatic watering for plants. I only use garden hose. Anyway, thanks for sharing this post. I've got an idea. Keep posting.

hose adapters

GotGSus said...

First and foremost, thanks for all the fantastic ideas. I've been kicking around the idea of self=watering vegetable container gardens for a few years now, but didn't really know where to start.
Thanks to this blog, I should be able to have some tomato plants going within the next week!

As for that Hudson valve needing a certain amount of pressure to work, I know from my Navy days that the higher you lift a bucket of water, the more "head pressure" you build up. I'm sure Google has the appropriate calculator within its' grasp for the correct height and hose diameter, etc. Might be the cheapest solution to that problem.

v/r,

Bill