Open Heart Surgery

For those of you who have been wondering, here are a few notes on various projects in the garden. You might recall (if you read my writings over on CV about a year ago on the subject) that I built a circulation system for the garden which drips water periodically at the roots of some of the plants. It has two control valves (one for the back and one for the front) that, after crawling around under the house with bits of string tied to my arms and a flashlight in my mouth, are connected by wired to a programmable timing device in the basement. Well this year saw me improve the system a little bit for the new season of heat.

I’d made one major silly mistake last year that as a physicist I should not have made. The pipes the run from the water supply to the pump (and are therefore under pressure all the time) were made of the same flexible black pvc as the rest of the system’s major arteries. most of the rest of the system is under leaves, dirt, or mulch, and therefore protected from the sun (and not under much pressure anyway) while this crucial section just sits there staring back at the sun all day. I happened to be home one day when the inevitable happened for the first time. The sun rapidly heated up and softened the pipes and the snug joints just slid open and there was water everywhere! If I was not home that day, hundreds of gallons of water would have been wasted (and poured into my foundations). Major design flaw. So I decided to do this year what I should have done then and replace the pipes with a heavier gauge white pvc, with secure joints.

I’d never done this before, and so I learned a lot that day. One of the things I love about this sort of project is how amazingly standardized all fixtures and fittings are. After wandering around the plumbing section of the hardware store for not too long, and consulting some sketches I’d made at home of what I wanted to do, it was pretty easy to get all I needed (various coupling joints, elbows, and lengths of pvc) to replace the old sections. Everything fits together snugly and one is reminded of ones childhood days of fun making things out of Lego, Mechano, and Better Builder (do I recall that latter correctly? does not seem to exist any more).

There was some fun chemistry as well. I was puzzled for a while about how I was going to put threads on the plain pvc pipes and joints I’d picked out. First, the male and female parts did not seem like they wanted to go all the way into each other without a fight to make a secure joint, which was a worry. Also, there seemed to be no threading machine (to make screw joints), and I did not fancy the prospect of having to buy one, in case it was expensive. Silly me. There’s an entire system of chemistry that makes the joints secure! You paint a primer (smells to me like it is primarily acetone, which some of you will recognize from nail-polish remover) onto the parts you want to connect and the pvc just softens in seconds. You coat both parts with an adhesive and then the now-soft parts can be pushed all the way into each other to make a secure joint using no more effort than available from a newborn kitten. Seconds later, the primer’s effect has gone and the pvc has re-hardened to its former strength, secured with the powerful adhesive, and the fact that it has re-hardened deep inside the snug region. Wow. Amazing what you can find on the shelves of the hardware store.
With this system, in a very short time I was able to replumb the system. I found upon testing it that there was still flow somewhere even when the system was supposedly off. After a while I traced this to the valve itself. Somehow (maybe because I had the pressure too high), it was not re-sealing itself very well. It was very instructive to open up the valve to see how it works, actually. Surprisingly simple mechanism controlled by a solenoid pushing down on a pin which makes a central unit rotate….. well, I won’t go into it. It was damaged.

I was worried at this point since I could no longer find the exact valve that I used last time, made by the same people who made much of the rest of the irrigation system. Did this turn out to br a problem? Nope. Standardization. After perusing the right shelves in the hardwarestore, I discovered that everybodys valves come in sizes that allow you to connect them to everybody else’s. And the voltage that the solenoids  work on match as well!

No major re-design needed,  I got a new heart for the system, and -after a bit of fiddling because there was not much space to move in the underground valve-control box I installed last year- I swapped out the old one for the new. Excellent.

In other news, you might recall (from an earlier post) my wondering what would happen to a surprise tomato plant that started growing out of a crack in the steps. I could not get it out without colling it and was sure that it would eventually just die due to lack of space, water, and nutrition. I was wrong! Here it is (picture right). I ate those very tasty cherry tomatoes for lunch the other day.

-cvj