16 July 2012

At First Flush

When we last talked rainwater collection, I had drilled a hole in the cistern to install the bulkhead, the black plastic fitting to which I would then attach the plumbing that brings water from the gutters to the tank.  (This project is teaching me lots of new plumbing vocabulary.)

So it was finally time to start attaching pipes to the tank. A vital component of any large-scale rainwater collection system is the "first flush," and since it's what actually connects to the tank, we decided to work on it next. This device catches the first of each rain before it comes into the cistern, keeping the dirtiest water (containing roof dust and any other debris small enough to fit through the gutter screening) out of the tank. This diagram shows how the first flush works:

 (Image from Earth Energy Unlimited)

We bought a first flush kit from Innovative Water Solutions (an awesome local rainwater/ graywater/drainage/irrigation company whose help has been invaluable on this project):

The kit included everything except for the regular ol' plumbing pieces, which I picked up at my local plumbing shop, Crump Plumbing Supply (really knowledgeable staff, and much better prices than Lowe's). The first flush system went together in pretty much the same way as the other piping I've been working on. Here it is (before I painted and permanently attached it):

Most of the plumbing is 4" pipe, but the inlet into the tank is 3" wide, so a reducer ("bushing," I think) was necessary to make the transition.  (I've been assured that this bottleneck won't interfere too much with the flow into the cistern.)  The left side of the T is still open here.  That's where the pipe leading into the tank will go.

At the bottom of the first flush, I added a 45 degree turn for easier cleaning.  There's a hole in the rubber dripper at the bottom that lets the water in the first flush slowly drain between rains.

The bottom screws off to reveal a long plastic strainer and the round rubber stopper with a hole in it (the kit came with eight stoppers with holes of different sizes for optimal draining):

(What you can't see here is the hollow plastic ball that goes inside the pipe, as shown in the diagram above. The ball floats up in the first flush pipe as the water level rises; a bracket holds it just below the T so water can flow freely into the tank once the first flush is full of water.)

Before I could permanently attach the first flush, I needed to assemble the pipe that would bring water up from the underground lines.  (I didn't want to be trying to glue pipe at the weird angles that would be required if I attached the pieces one by one.) Once that was done, I painted the whole assembly with hammered silver spray paint (to approximate the look of the tank and the metal roof)...et voila:

Next up?  Put in the underground pipe between these pieces and the first downspout, then expand outward from there.  We're also working on the line from the tank outlet to the pump, and I'm scouting supplies to build the pump house (we're shooting for an aesthetic similar to the house house).


  1. Looking good Devon!! Keep it up, you are almost there!! I love how you are documenting the process. I will be referring clients to your rainwater collection system installation series in the future so that they can see just how much work goes into one of these systems.

    1. It's SO much work! Way more than it seemed like on the front end....

  2. what paint did you use on the pvc? i've ordered the same tanks and need to paint my pvc to match. thanks.

    1. It's Rustoleum's hammered silver spray paint, although there aren't many "hammered" spots. (Basically it's just silver.) Hope that helps!