More Reliable Pump Construction

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
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CDMT
Posts: 76
Joined: Mon Oct 20, 2014 11:35 pm
Location: Hawaii

More Reliable Pump Construction

Post by CDMT » Sun May 24, 2020 3:19 am

This guide will show you how to quickly and easily assemble water gun pumps of slightly greater than ¾” pvc pipes that operate more smoothly than typical homemade pumps. The benefit of using this pump is that it pumps smoothly, reliably, and can reach pressures of at least 118 PSI. Handheld you should be able to pump your water gun easily up to 70psi and 80-100psi with some effort. I am sorry that I did not make this guide sooner.
If you are interested in making this pump I would order one of the Three tube water guns used in this pump sooner than later as the company that makes them does not seem like they have a steady distribution. Below is a picture of a water gun with one such pump installed:

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Materials-
1- Gardena 36917 Hose Connector - Tap end:
https://www.amazon.com/Gardena-36917-GA ... B00004SDYI
1- Gardena 36002-G Faucet Tap Connector:
https://www.amazon.com/Gardena-36002-Ga ... B00L592JK4
1-A single tube taken from Three-Tube Water gun from eBay:
https://www.ebay.com/itm/Three-tube-Wat ... 3081254700
1-3/8” x 36” aluminum rod:
https://www.homedepot.com/p/Everbilt-3- ... /204273962
1-3/4 female garden hose to 1/2 MIP adaptor:
https://www.lowes.com/pd/b-k-3-4-in-thr ... lsrc=aw.ds
1-female hose to male Quick connector:
https://www.amazon.com/Orbit-58089N-Pla ... B0040QWOIQ
1-3M marine adhesive sealant fast cure 5200:
https://www.amazon.com/3M-05206-Marine- ... 567&sr=8-5
1-roll of Teflon tape:
https://www.homedepot.com/p/1-2-in-x-26 ... /204286187
1-roll of duct tape:
https://www.walmart.com/ip/3M-Extreme-H ... gIVZ_D_BwE
Tools-
Dremel with a standard sander, cutting wheel, pointed grinder
Channel locks
Needle nose Pliers
Scissors
Vise
PVC Pipe deburring tool
https://www.homedepot.com/p/Imperial-3- ... lsrc=aw.ds

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First take the three-tube water gun and cut it into 3 separate pumps lengthwise using a dremel or hacksaw. I made this guide using the earlier single tube water gun. The only difference is that they have decided to connect three tubes into one tube. Then secure one of the tunes in a vise very lightly to avoid denting the outer shell of the aluminum tubing. Next pull the plunger back and cut off the water gun’s nozzle with a Dremel and discard.

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After that is done next go around the cut portion and deburr it and remove enough debris that you can easily push the plunger out.

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Next take some small needle nose pliers and carefully pull out all the tacks securing the plunger head. The plunger head should be saved and the rod discarded since it is thin easily bent metal.

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Next take your cut tube and stick it it next to the water gun whose pump you want to replace and figure out how long you want the pump to be and mark it with a permanent marker. Then carefully spin the tube around marking where you will cut it. If however you get lucky and the Chinese factory has failed to glue the plunger guide as in this example then simply pull off the plunger guide. Then line the smooth side where the plunger retainer had been to the start of where you want the pump. Then simply cut off the excess with the Dremel like before.

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Next you will take the ¾” Orbit garden hose male quick release and tighten the male insert into the vise.

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Next take the Dremel with a course sanding attachment and widen the inner diameter so that it can fit snugly over the pump tube. Typically I will take the quick connect out and rotate it around periodically to get a more even fit. You should start the Dremel on the lower quarter of speed so that you don’t immediately melt the fitting. You must also take care not to make the outer walls too thin. Periodically I will see how close it is to fitting over the aluminum tube of the water gun pump. When it gets close to being the right size at that point I will increase the speed to where it will melt a little and then I will quickly push the tube in. Next you need to turn the insert around n the vise lengthswise. Then using the dremel with the cutting wheel cut the male insert off that was holding the fitting to the vise. Then complete the widening of the fitting all the way through to the other side so that it snugly slides over the aluminum tube of the pump.

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Next take the deburring tool used to clean up PVC fittings using the pointy end meant to clean up the inner part of pvc pipes and press your tube into it firmly while rotating around so that you evenly flare the tubing. It is important not to press too hard but just firm enough to slowly bend the tube outward as you rotate around.. The flare should only be big enough to prevent the Orbit fitting from coming off but not seriously impede the threading of the fitting. The point of doing this is so that when you tighten the fitting it can push the tubing into the O-ring of the Gardena female hose fitting thus sealing it out. This is why you also want to use the straightest cut end of pipe for the portion that will be flared.

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Once you are done with flaring the next step is to measure out a length of 3/8” aluminum rod which can be bought at Home Depot and cut it to length with a Dremel. Then take the plunger and squirt some 5200 epoxy onto the rod and inside the plunger’s rod holder and press it onto the rod. Wipe off the excess and let it sit for 24 hours in a well ventilated area. The next day if your Three-tube water gun's rod guide was not glued, slide it onto the rough end and then tape it secure with duct tape which will make it easier to replace the plunger after it wears out. Then slide the plunger rod first into the large flared opening and out the rod holder. Next tighten the flared end into the Gardena Quick connect. Then measure out a length of 1” PVC pipe from the fitting to the plunger guide and cut it to length in order to protect the soft aluminum of the pump from dents. Then take duct tape and wrap the aluminum pipe near the fitting and at the plunger so that the 1” length of tube you cut can slide snugly over the outer shell of the pump.

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Then duct tape it in place taking care to lock out the pump’s quick connect as well. The reason that I use the Gardena quick connect is that it has a rather generous sized seat for the o ring that prevent the o-ring from slipping out forming a good seal.

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Finally after wrapping the Gardena quick connect threads in plumbers tape screw it in the brass fitting that converts the threading from Garden hose to PVC threading.

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SSCBen
Posts: 1616
Joined: Sun Jul 04, 2004 4:15 pm
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Re: More Reliable Pump Construction

Post by SSCBen » Sun May 24, 2020 7:46 pm

Great work! Using manufactured pumps would be far more reliable. I'll probably do something along these lines in the future.

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