Introduction: Check Valve / Rücklaufventil From Recycled HDPE

About: I studied Design and Context, Education in the Arts and Fine Arts (Department of Photography) at the Academy of fine arts Vienna. Have been teaching 10+ years since then. I love sailing, kayaking, canoeing an…

Recently I've become more and more interested in plastics. I startet collecting HDPE caps and bottles and bought a micro-oven to melt some down.
I had this block of HDPE sitting around for some weeks now and just showed it around at work thinking about what to do with it. I machined some

on my even newer Chinese Mini-Lathe and tried cutting and planing it. Last week I started building an injection machine to create parts for kicker tables (we got some at work/school and the pupils keep loosing

balls...molding your own balls, glide sleves, grips and figures would go a long way----originally I thought turning balls on the lathe would be

nice but you need a ball turning jig and molding should be fun for the kids too).

Then something other comes along...I got a pump that extracts condensate from the gas burner up 2 meters. The water keeps going back after every

pump cycle so I figured I needed a check valve (Rückflußventil). So here we go.

The basic design is a tube with a marble inside which closes a hole when water is running back. Instead of the tube their could be a flap. I just love those basic principles. There is a video about the craft of building wooden pumps which you should watch if you want to someone

making a pump from a tree. He uses leather for the valve flap. There are more episodes of the programm called "The last of his trade" (Der

Letzte seine Standes) and well worth watching.

Step 1: Recommended Tools

HDPE melted down in a tube or rectangular stock like I had on hand


drill bits (I used a 9mm and a 20mm + a sinker)

a marble or some steel ball that can close the diameter of your tubing

some aluminium tube your hose will fit over.

solder iron for welding the parts

Step 2: Let's Get Started

Start with drilling the holes.
I did drill a 9mm hole and countersunk it a little. The other two parts start with a 20mm hole and a 9mm hole. one of them is then finished with holes or cutouts around the 9mm hole.

After cutting out the parts on the bandsaw I did some touchup on the lathe to help with aligning the parts for welding. A small camfer on the edge between the parts helps with welding. Better start round stock. The lowest part with the 9mm hole was only cut on the bandsaw as there was no way to chuck it up fast on the lathe.

Step 3: The Aluminium Tubes

The aluminium tubes are melted in. They are 10mm and I purposely only drilled 9mm to have a nice fit.
Clamp the aluminum tube in a vise and heat it up with the blowtorch. now just press your part on. Repeat on the other endpart.

Now put in the ball and suck on the tube to see if it closes properly. If not use the countersink to repair the edge of the hole or rub around the ball until it closes properly.

Step 4: Welding the Parts

Now weld together the three parts ...!!!don't forget the marble!!!...
Use a hot solder iron or heat up some metall with a blowtorch. you can feed in some HDPE material if you like but there should be plenty of material.

Step 5: Test in Install Your Valve

The valve needs to be installed with the marble in the lower part. Gravity helps close it properly. Also install it at a low point if you use it
in a vertical hose to have a water colum above the valve.

Let the pump do it's work, switch it off and pull off the lower hose. Mine is working just fine.

Thanks for reading till the END :)