Katie's Questions About Irrigation

Hi Matt,

I've been checking out your green wall blog for quite some time preparing to build my own green wall. I really like the Patrick Blanc style wall system in your I was wondering if you could give me more specs about the irrigation you used. I saw you said it was rubber hose, which would work for me as I'm trying to keep my costs down... could you tell me more? Also, any other info you may have would be fantastic. Thanks!

Katie

Hi Katie,

The tubing I used was PVC tubing. As I have mentioned before I wouldn't use PVC again because it is a toxic plastic although it is quite common. I would substitute an inert plastic like polyethylene. Something like this.

http://www.amazon.com/Polyethylene-Tubing-Wall-Working-Pressure/dp/B000FN10CO

I used a pump similar to this one.

http://www.garden-pond-supplies.com/Pondmaster_Magnetic_Drive_Pond_Pump_MD_12_p/02712.htm

You'll need adapters to connect all your tubing to your pump. Depending on what setup you chose you'll need a few L connectors and possibly a T connector. Also you'll need to step down sizes if you use thicker tubing for the vertical. Read on for an explanation.

Ideally your pump sits at one corner of your basin and pumps water up to the top of the wall where it pumps across the wall and trickles down. That would make an L shape if you were looking at the tubing on the wall. You could also locate the pump in the middle of the wall and split the tubing to either side. This would form a T. The advantage of the T shape over the L is that you could balance pressure a bit better. In the L shape the holes closer to the pump get more pressure and thus more water. The further you get from the pump the less pressure and the less water. If you use emitters

http://www.dripirrigation.com/index.php?cPath=38&sort=2a&page=3

...then the flow can be balanced by the emitter. I didn't use emitters and I don't know much about them. I just know that they can balance flow. For my wall I just drilled holes in the tubing and used very low pressure. I also slope the tube down slightly at the end to use gravity to even out the pressure. Setting up the water pressure is one of the trickier parts in a greenwall.

I have mentioned before that I could probably have used a smaller pump that cost less but how much smaller I'm not really sure. The aquarium store that sold me the pump said I could return it if it was the wrong one. You may want to find a store willing to do this. Also be careful about recommendations from the aquarium store. They require much more pressure in their lines then a greenwall does. For that reason they recommended a pump that was larger than I really needed. If you use emitters you'll need more pressure. The irrigation store you get the emitters from can make a recommendation I'm sure.

The aquarium store did recommend a much thicker pipe for the vertical tube. I'd say the tube was about 1.5 inches ID (interior diameter). The idea is that pushing the water up to the top of the wall requires the most force so you want a wide tube to increase the flow and lessen the pressure. I followed their instructions but I am not completely sure it was necessary.

I drilled holes on both sides of my tubing (front and back) with holes every 4 inches as described by Patrick Blanc. In future I would only locate the holes facing backwards (towards the wall) because at times forward facing holes have led to drips off leaves.

Blanc describes the irrigation holes as being 2mm. I'm not sure if I converted that to figure out the right drill bit size. It was to my memory about the size of a pencil lead. Maybe a bit smaller.

Your pump will come with some kind of filter sponge and I highly recommend you use it. It doesn't take much to clog the small holes. Be very careful when you plant your wall to get as little soil/debris in your basin as possible. If possible install the basin after you plant your wall.You may want to consider some kind of inline filter as a back-up. The filter on my pump came off once and I had to take the tubing down and clean the holes out by hand.

I use a digital 7 day timer to water my wall. This is the timer I use.

http://www.intermatic.com/products/timers/consumer%20outdoor%20timers/digital%20timers/hb88rc.aspx

This timer is easy to program and you can set multiple very short intervals as many times a day as you like. Although it's a seven day timer I have it set to water the same times everyday. So you could probably use a digital one day timer too. I water 4x a day for 10 minutes.

I'm not sure how soon you plan to build your wall but if you can wait about a month I will have my fully documented wall build online. If you have any other questions please let me know.

Matt