For a few years now, my friend Ron has hosted a summer water slide party at his house.  Initially, it was a plastic tarp and a garden hose, and has sort of evolved from there.  This year, the plan is to run a 6-8′ wide billboard tarp as a slide-way, with a plywood-reinforced splashdown pool, and a pump capable of over 3000gph to recirculate water in a closed system. With the party looming and lots of other things going on, Ron has drafted me to help with some of the “plumbing”, including a pick-up strainer and a water diffuser for the top of the slide that won’t cut people in half with the force of the water.

On the next page, I’ll describe the circulation system, and have some photos of the parts we’re making.

Basics

First things first: This pump moves a MASSIVE amount of water.  I was a bit confused about the capacity at first, but Ron helped me to understand. (his is actually a 1.5″ model, which moves more like 4000ghp). We’d talked about testing the pump and its fittings in a bucket of water, but found a slight problem with testing on such a small scale: this pump will empty a 35 gallon garbage can in around 20 seconds. To that end, rather than testing, I ran some calculations to determine what the total “hole area” our fittings needed to match the 1.5″ diameter of the hoses on the pump.

Surface Area of 1.5″ Diameter Pipe = 1.8 sqin

surface area of a 1/8″ hole (.125″) = 0.01227 sqin (150 holes)

surface area of a 3/16″ hole (.1875″) = 0.02761 sqin (65 holes)

surface area of a 1/4″ hole (.25″) = .04909 sqin (40 holes)

surface area of a 3/8″ hole (.375″) = .1104 sqin (16 holes)

surface area of a 1/2″ hole (.5″) = .1963 sqin (10 holes)

Those calculations all assume a “1:1 pressure factor”, ie we’re not building any pressure by restricting the flow of water. Water in the main line will flow approximately 14fps, and with those figures, so will water through each hole. In practice, we ended up drilling far more holes than that, so our pressure factor is greatly reduced.

Pickup

The “pick-up strainer” is simply a fixture to go in the splashdown pool and serve as a first line of defense to prevent foreign objects from ending up in the pump.  We took a piece of 1-1/2″ PVC pipe (around 18″ long) and perforated the bottom 2/3 of it with around 30 1/2″ holes.  This will put us at a 3:1 ratio, slowing the intake speed to around 5fps at each hole.  Further, the entire fixture will be wrapped in window screen to filter out even smaller debris, while also reducing the flow (so we’re effectively maybe 2:1).  Also, it will hopefully prevent anything important from being sucked into the pump.

Fittings

To transfer the water from the splashdown pool back to the top of the slide, Ron bought 3 25′  Flat 1.5″ HF discharge hoses. Theses hoses had no fittings on their ends, so we had to add some of our own.  We picked up some hose-barb to screw-thread fittings (around a buck each) and slid them into the ends of each hose (male and female each). I found that a bit of lubrication made installing the fittings much easier.  Windex seems to be pretty slippery, while also not eating the plastics.

There’s also a 7-10′ section of 1-1/2″ pool suction hose that attaches the pick-up strainer to the pump.  This hose is spiral-wound to withstand the force of the pump trying to collapse the pipe through suction. It’s also crazy-expensive (around $3.50/foot).  I know that worm-screw hose clamps aren’t the right way to attach the fittings, but they’re what we had.  These fittings needed turned down a bit, as the barbing on the outsides was too aggressive, given that the ribbed tubing is almost completely inelastic.

Discharge Fixture

“Discharge fixture” is just a fancy name for a piece of pipe with a bunch of holes drilled in one side. We stuck with half-inch holes, but put them closer together (on 1″ centers, for a 50% hole-to-plastic ratio), and drilled around 40 of them in a 48″ section of pipe.  This puts us at 4:1, and hopefully reduces the water velocity enough that it “gushes” rather than “sprays” (scientific, I know).

Photos

I know I’m missing photos of the pickup and discharge fixtures, but I didn’t think to take any while I was building them and they’ve already been delivered to Ron’s place for the party in early July.  I’ll definitely have more photos soon, and will update this post when I do. In the meantime, some photos of the plumbing…

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Projects by Kevin