Thursday -D3P1

For me, Thursday was the beginning of the real work. We had created a basic plan to replace the first flush system as early as Tuesday night by taking out the old horizontal pipe (4" PVC schedule 40) at the ground level elbow and splicing in an equal horizontal length about 30" higher off the ground and rotating it 90 degrees to run along the side edge of the pavilion between two of it's concrete cement supports. The splice would incorporate a "T" union and keep the lower length down to the elbow which would act as a weight bearing column.

What We Wanted

Please remember I am not a visual person and this is not exactly autoCAD. This design seemed to meet all of our demands: It got the pipe up off the ground; it replaced the same approximate storage volume; it moved the small drain hole higher out of the dirt and vegetation. In fact, we could salvage most of the needed PVC piping from the old parts. The only thing we needed was a pair of 4" Ts and four 4" clean out caps (remember, we are replacing two of these systems, one on the east and one on the west side of el rancho). These items were present on the shopping list when Mike and I went back to Isla Colon to visit our good friends at Maderas Richards. A small problem arose when Richard said he did  not have any 4" Ts; he suggested we use 3" Ts and a 3"-4" reducing bushing on each side. I was not comfortable with this as the contraction would from 4" to 3" would slow the flow rate and increase the pressure across bushing. It would also add more couplings, which in  turn, means more places for failure. What Richard had as an alternative was a 4" 45 degree "Y"; this eliminated the need for reducing bushings and all of the hydraulic mayhem it created. In the moment it seemed like a fine solution so we bought a pair of the "Y"s and brought them home with us. Also, unbeknownst to us, Richards had failed to load all of the galvanized corrugated sheet metal (colloquially known as "zinc" in Isla Popa and the environs) so when Mike and I pulled out from the dock, we were missing several sheets of zinc. Not a crisis but what would later become a hassle.

We freighted our stuff back to the island and on Wednesday and on Thursday Chip and I began knocking together the first flush system while Frank continued to process water samples and Tim began the job of fixing the gutters. Just to clarify further, while each of us was doing our own respective tasks, we would frequently drop whatever it was we were doing to help someone in a more critical phase with whatever they needed.We started by sawing off the bottom horizontal pipes and replacing them with a 4" stump that we covered with a cleanout cap. As you can see in the above sketch, the section below the "T" piece remain intact down to the elbow to support the entire PVC tube column up to the roof, so that it doesn't pull down on the roof gutter or straps. We next had to cut the former straight section out and replace it with the 4" "Y" sections. The question was how to orient the "Y", upward or downward? We opted for upward so that it would be symmetric with the upper pipe (the"aesthetics argument"). In fairness, we did not give it enough consideration from the geometric and hydraulic perspective which would later come back to haunt us.

What We Did

The problem with this configuration is that once the water rises in the lower column to the level that is higher than the crotch of the "Y" air is trapped in the horizontal limb with no way of running out,  as water stays at its lowest level and air at it highest. As the column fills with water, there is no escape for the air, staying trapped along the upper half of the tube in effectively, a bubble, unless some way is found to vent it. A little foresight and better investigation would have revealed the conclusion that putting the "Y" in "upside down" would have eliminated all these problems.

What We Should Have Done.

This design would have allowed the water to run down into the "Y" at the same time that uphill traveling air would have exited the pipe possibly out the flow tube out into the tank itself. Our failure to appreciate this meant that we either spliced the "Y" back out and turned it upside down or we would have to create an air purge line at the left end of the pipe in the cap. We opted for the latter.

In these photos the revised first flush systems are all up and in position. We are viewing the west side of the pavilion. Note the assembled revised first flush system on the far (east) side of the building. Several other things are worth mentioning in this photo. The first is the fence that can be seen just to the left of the large zinc clad 600 gallon tank. The fence terminates in a post which virtually blocks that location from being used as the site for the 40 gallon secondary barrel (imagine the smaller, horizontal tank on a stand nested to the left of the tank.This was the original plan. Now look at the lovely space to the right of the big tank between it and the elements of the first flush system. This space is where the barrels would eventually go, but not without it's own set of complications such as requiring a large number of 90 degree 3/4" elbows to make the turns under the tank and back up into the side wall of the smaller tank. Lastly, note how much better the gutters are snugged up to the roof. This is thanks to the efforts of Tim (and various others) who improvised a phenomenal technique for holding the pipe fast to the roof while Tim added or tightened metal strapping to support the gutter.

We will discuss more of that, Frank and water testing,  and Mike, Elizabeth and Marianna assembling the tank stands when I resume. Still way behind schedule, but getting some momentum going now.