Irrigate'n with Cistern Water

Been wanting to do this since The Cistern was contemplated. It's just been kind of about now that all the pieces have been in place to see how it works.

Big problem was infrastructure to serve cistern water to the irrigation system at or near city water volume and pressure. The pump with the pressure control valve finally working gives us more or less city pressure. Not great volume, but washing the car from a hose connected to The Cistern pump distribution system suggested it might be enough to prove the concept. 

By the way. A Volvo washed with rain fresh cistern water is a shinny car indeed!

A not insignificant longer term problem to address is what to do if The Cistern runs dry. There is a thing called a "genius switch" that will detect cistern flow and then automatically switch over to city water. Genius switch seems just a bit presumptive, and they are quite proud of them. Like multiple thousands of dollars proud. Frequent readers may recall I subsequently identified an Australian thingy that is essentially a toilet float for $100US that will fill the cistern automatically if the water level runs low. Low tech, but would require some plumbing. Better to prove all this works first. In our last muse, you may recall in the Testing of The Cistern vent, we also proved we could fill The Cistern by throwing a hose into the roof gutters and opening a hose bib. Not elegant, but effective. Good enough for now!

A related and critical unknown is just how much water an irrigation circuit requires. If we're constantly throwing a hose on the roof to fill the cistern, why bother? In theory, if we had kept track of all the emitters on each irrigation circuit we could get a good estimate. But that ship sailed a long time ago. I suppose I could stick my head in the water meter pit, but given the terminal nature of bugs around here, I'd rather take a pass on that technique. Guess we'll go empirical and just watch the cistern gauge...

So unknowns identified and in-hand, now the big gut check was cutting the perfectly good pipe running from the city water tap into the irrigation distribution boxes. A little shovel work, which is never easy at the Quail Manor, exposed all the piping. One well placed cut will be good for a test and position us for permanent plumbing if this works. And, as is Tucson standard, a pipe is considered buried when you kick some dirt over it. So not a lot of shovel work was required.

I cut the pipe and learned the irrigation guy was no better plumber than The Cistern guys. The cutting broke the next joint down. As we used to say in the coal mines; if it's easy you must be fucking up. Or as we said in the cynical world of management consulting; if it was going to be easy, they would't need us. By the way. If you watch House of Lies on Showtime. It's more or less recognizable as kind of what we did. But we had WAY LESS sex. Way way less. A further aside, in one of the early episodes my Firm (which will remain unnamed, but they tell us we are "partners for life" so I suppose it is still "my" Firm) was mentioned specifically has a den of vipers. Seemed apt.

So, nothing is easy. I rifled through my limited but growing supply of plumbing small parts left over from prior projects. And found exactly what I needed to attach a hose from The Cistern pump distribution system into the irrigation system. And fixed the broken fitting.

With SWITBO's oversight, we fired up the pump and ran a circuit. Sucker worked fine.

Using the gauge system with before and after Gauge Cam snap shots, and some cipher'n, determined we had used 122 gallons running each zone for 10 minutes. Extrapolating, a normal summer time 60 minute cycle would require about 732 gallons (that's 31.2% of cistern capacity). This could be a problem. We (OK, she) really wanted to run 30 minutes so her plants get a good drink. And more data points are always good, So we started a 20 cycle. In the first run, we'd notices a whooshing noise over by DnT's. Couldn't find any evidence of a leak so attributed it to I guess is just goes whoosh over in that area. In run two, SWITBO found an repaired a leak. 

We restarted. The 20 minute cycle required only 130 gallons. Recollect that next time you get an irrigation leak. They use a whole lot of water! So this suggests a 60 minute cycle will use closer to 390 gallons (about 17% of cistern capacity). Closer to a number we can work with.

Further, the experiment learned us that maybe we cistern irrigate when we're in residence and city irrigate when not. There are a lot of semi fragile moving parts in the cistern pump infrastructure. The failure of any one of which would be a big pain to address remotely.

Which informs how we do permanent plumbing. The going back and forth between potable (city) and non-potable (cistern) water.

Many designs were considered. At issue is that by code, and just a good idea, we need to isolate non-potable water from potable. There are a couple of techniques. Simplest was just to put a piece of hose on the end of the irrigation pipe and connect it to either the city or cistern. That way only one system is connected at a time and they are thusly isolated. Or you can have an "air gap". That is how the Australian toilet bowl thingy works. Or an anti-siphon valve. Which we already have. All irrigation systems have them, or at least should. When at the Depot, I also found a check valve.

So conceptually, with a check valve, then a ball valve, and finally the anti-siphon valve, we have triple redundancy between potable and non-potable water sources. So I feel comfortable connecting the two systems with permanent plumbing so the choice of water source and switch over is trivial.

Here is the winning design concept. The pipe next to the wall is from The Cistern Pump Distribution System. It tees, takes some elbows, and comes into the left side of the box, through a ball valve (shut in this picture) and into a tee to the irrigation system. The pipe coming into the right side of the box is city water. It comes though a ball valve (open in this picture) though check valve that is under the ball valve handle and into the tee to the irrigation system.

Irrigation set to take water from the city.

Irrigation set to take water from the city.

The yard stick and Ann's foot are for scale.

Switching between city and cistern water and running the irrigation system confirms our pump flow is a bit low. I'm guessing if we were going to water for 30 minutes off the city, we'd probably water for 45 off the cistern to put the same water at the base of the plants. Have not measured this and don't plan to.

Given the funky grades on this side of the house, we had to place the source switching box pretty high. As a result, the lines in and out are less covered than I like. So I insulated them. The black pipe on the right of the picture is the city water going to the irrigation. That was insulated by Bob the Plumber with foam and Gorilla Tape. Bob the Plumber preferred Gorilla Tape over Duct Tape (the handy man's secret weapon) like a lot. The Gorilla Tape keeps the sun from eating the foam. I did notice it was drying out a bit, so will probably retape next year.

Anyway. When I went to get foam, I was afraid it was so thick I would not be able to bury it. So I got some dense rubber insulating tape. Then I remembered there was some Foil Tape left over from the installation of the HVAC system. As if my habit, I did not throw it away, but had no idea what I was going to do with it. Until now! But first I used electrical tape on the elbows to secure the insulating tape using a technique similar to taping bicycle handle bars around the shifters and the drops. I'm not very good at it on bikes, but plenty good for buried pipe in The Bario.

What I love about all this is; it looks like something NASA would build to pump fuel into a rocket or something. Concealed just under the A Mountain rock and dust. Future Archaeologists will go crazy trying to understand the meaning... 

The irrigation line exiting the box is similarly insulated.

That's a whole lot of tape technology engaged in insulating pipes that might see a freezing temperature for 10 minutes once a decade. I'm guessing no one in Tucson would be insulating these pipes, they are technically buried. It's not easy being me.

Meanwhile, Dave the Welder has finally returned and is progressing the cantilever gate on the front courtyard. Frequent readers, and I mean frequent and careful and detail oriented readers may recall one of the fasteners holding the top rail to the courtyard wall popped loose.  Thinking was the masons had not properly grouted the cavities in the cinder blocks. But to fix it was going to require taking everything down and starting over.

DTW came up with a plan where a 1.5 inch hole was cut around the offending fastener, investigation would ensue and grout would be pumped into the cavity using a grout bag. Now, a grout bag is identical in all respects to a cake piping bag with one important difference; it is WAY more manly. So the hole was drilled. And drilled. And drilled. The cavity was grouted perfectly, thank you Tony the Mason. Problem was given the vagaries of block laying and cantilever gate building, this one fastener ended up at exactly the interface between the top of the block and the bottom of the bull nose (the curve along the top of the wall that makes it look southwestern) and the bull nose popped. It's decorative so it's allowed to pop.

So. A 12 inch deep hole was drilled through this wall and into the abutting wall, which turned out to also be fully grouted, thank you Tony the Mason. This hole was then filled with epoxy into which a threaded rod was inserted. To which a bolt was attached to replace the failed fastener. 

All this took several days. And the result looks identical to where we started. But it's now secure as hell.

Getting all this done establishes exactly where the gate will hit the house wall and where the jam needs to go. Trouble is Dave is Dave and stucco tends to settle towards the bottom of the wall when applied, it's a gravity thing, so the wall bows out a bit at the bottom. The channel that makes up the jab is 3 inches by 4 inches and strong as hell. There be be no bending. But there will be scribing. So Dave scribes the outline of the wall on to the jam and proceeds to cut it to match. This is some heavy shit. Sparks fly. Blades get broken. But the damn thing fits just like Norm Abrams and Tommy Silva from This Old House were building cabinets from some kind of wimpy wood. And. Then we welds a new back on to the cut channel so it is enclosed and bugs and things can not crawl in to set-up residence. It's a marvel. That is now off being ground so you can't tell a new back was welded on...

In the fullness of time, maybe tomorrow, this gate of magnificence will be complete!