The Cistern Mystery: Addressed. Tested. Resolved.

Frequent readers, and if you're still reading these things, you're a frequent reader. Will recall that in an earlier installment, we identified a kind of big deal that the cistern overflow had no vent.

Well by god, it does now.

Your musist did some research. Went online. Googled. It turns out there are all kinds of vents. The literature describes the characteristics of each vent type (there are amazingly five of them) and at the conclusion of each description says: 

an individual vent should be at least one-half the size of the drain it vents (no less than 1 1/4", 32 mm)

The officially recognized vent types are; individual vents, relief vents, circuit vents, branch vents, stack vents. Now cistern overflow is not one of the officially sanctioned vent types. But, since they all go one-half the size of the drain and no less than 1.25 inch and I have a 3 inch drain, I figured with a little engineering I could come up with something. 

A P Trap

A P Trap

An issue is keeping foreign objects from falling into or onto the vent. Or for that matter something building a nest. From an iteration of the cistern gauge project, I conveniently have a discarded 2 inch 180 degree elbow. It is intended to be used at the bottom of a "P Trap". A really big "P Trap". And I had a nice length of 2 inch pipe. So I did some cipher'n and determined that was at least one-half of a 3 inch drain and more than 1.25 inch. There's our vent diameter. 

Off to the all mighty Depot to get parts. I was figuring a tee and some fittings to get from 3 inch to 2 inch. Careful observers have already noted, Musist, that is a really clean 3 inch tee to 2 inch transition you have there. Right there on the shelf was exactly what I was looking for but did not know existed. I thought providence. Mom will attribute to a higher deity. However you get there, that is one clean transition. And I get to reuse parts already in inventory.

There were some challenges getting the repair made. Doctors have their Hippocratic Oath. Fix-it guys have a derivative oath that goes along the lines of don't fuck-up but for sure leave yourself a way to go back to the way it was before you fucked-up. The obvious choice is to just cut the old elbow off at the horizontal pipe at the top of the old U. But if I do that I'll be able to glue a new piece on, but only once. If I start messing with the stand pipe on the left of the picture, I start having to drain the cistern. 

So I split the old elbow instead so I could pull it off the horizontal. To which it was glued like a mother. Our rainwater harvesting guys did a nice job, but neglected to glue a couple of really critical joints that are going to be horrible to fix. But, they glued the shit out of a joint that by design will never see water. So I made a couple of cuts. Chipped out a piece. Then chipped out another piece. And so on for the next 30 minutes. Then filed down the resulting mess so my new fitting would go on.

While we had access. The horizontal pipe coming around the cistern from the right. carries water from the north side of the roof back to the cistern. The rainwater harvest guys glued it well enough, but left around 10 feet unsupported. I could do some more ciphering, but 10ish feet of 3 inch pipe full of water is not an insignificant weight. That weight is suspended on one end by the leaking tee coming out the ground. That turns into a bending moment that pulls the stand pipe out of vertical. And pisses me off.

So while we had access I figured we lift the suspended horizontal pipe to get the stand pipe straight and throw a support under there. Well, like I said, it was heavy. This boy, and his wife, and a lever weren't moving that pipe. At home, I'd just go get a jack. At this home, no jack. After some pondering, remembered that there IS a Volvo with buttery soft leather AND a spare tire WITH a jack. Worked great. 

Unfortunately, the jacking and straightening and cutting and chipping and filing and pounding, did the leak no good at all. Became more of a flow. Now what...

The Barrio has a neat old Ace Hardware. Close by and old school. Not a big selection, but most stuff you need. I go over. Fortunately a couple of the proprietors are hanging near the front door. I explain the situation. They nod and go "hummm" during the telling at the salient points. Then they speak among themselves testing and discarding alternative solutions - none of which are met with much enthusiasm. We all know the best we can hope for is to slow the leak. Finally I am consulted again. Do I want something temporary and less likely to work or something more permanent with a more optimistic outcome.

We head into the store. To a shelf with JB Weld. Ha. I should have thought of that. But it's not just any JB Weld, it is WaterWeld. Will dry under water. Problem is there is some pressure inside the pipe which will make it unlikely we can actually get the weld INTO the pipe to stop the leak.

Which turned out to be true. Being unsure exactly WHERE the leak was I went around the whole circumference of the fitting. Then I learned it was actually leaking from the other end of the fitting, which was fortunately close by. So I did that too. Then I learned it was actually leaking from the back - inaccessible - side. Of course. So. Relying on my coal mining heritage. I used the whole freaking tube. Kept mixing and packing and mixing and packing until it was gone.

Next morning it did in fact dry, while wet. And the leak is slowed back to about what it was. And, we have a nice white band, according to the instructions it is off-white, but looks pretty white to me. And, as her Sweetness has observed, going to be hard to get paint to stick to THAT.

We'll use as much cistern water and hope to get it fairly empty, then drain it, and then have a real plumber come in and rework the whole overflow approach so there are NO LEAKS and the pipes are properly supported and everything is plumb and level. At the same time we will add what is necessary to fill the cistern from city water and connect the irrigation to our cistern pump and stop irrigating off the city. Will wait for the cistern to empty.

But first. Since the cistern was about 75% full and the overflow while theoretically well designed and executed, was untested. So. I threw a hose into the north side gutter and one in to the south side gutter and filled 'er up. Now the level of the overflow is the result of estimating line loses and using a laser to site off the bottom of the south side roof gutter since it is the lowest. Key word there is estimated. So to get two tests out of this exercise and measure the maximum capacity of our system, I plugged the overflow.

Took WAY longer to fill than you would have thought with two hoses going full blast. It filled and filled and filled. Once the gauge showed full, I'm down at the cistern using the raise the hose until water stops coming out technique. Once the south side roof gutter started overflowing, we had added 9 inches to the capacity of the cistern! Which is about 270 gallons. Takes us from having about 80% of the cistern's actual capacity to about 90%. When you figure in the volume of water stored in the pipes (that we did not plan on), we will be using about 94% of the stated capacity of the cistern once we replumb the overflow. Which is cool.

Then I removed the overflow plug. A 3 inch pipe running full is a pretty impressive force! Took a surprising amount of time to drain down to the current overflow level. I'm continuing to monitor cistern level with the hold up a hose method. The overflow stopped exactly as intended.