Build a homemade water gun or water balloon launcher and tell us about it.
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Post by C-A_99 » Sat Jun 05, 2010 11:01 pm

Well, I just went out and tested my CPH for the 9000th time or so, and it worked pretty much perfectly, something I've never gotten a homemade water blaster to do. (Except for a 2" waterzooka-style homemade.) For the pump, I went with a considerably different approach.

I used the 1/2" aluminum rod. Wooden rods do not seal with the O-rings well and every single time I used them they've been a bad choice. With the 1/2" aluminum rod, I used 1/2" ID, 5/8" OD O-rings. You want O-rings with the same ID as the rod and with 5/8" ID for 1/2" sch. 40 PVC. This may seem like common knowledge, but it's very important. If you have trouble getting the O-rings to slide, use silicone grease, which is great for pumps and ball valves. I also have a spray-based silicone lubricant which I use for tough-to-reach areas, such as with water gun internals.

Now once you have your O-rings, you need spacers of course. Merely sticking glue onto the O-rings to hold them on is no good, which I actually tried when I built a pump for the first time.

There are several other choices; CPVC and tape are the most common. Electrical tape, duct tape, and gorilla tape all work the best, but they really do not hold the O-rings on very well since they wear out over time. However, they line up very well unlike CPVC which needs to be cut perfectly square to get good results.

CPVC in my experience has not been a good choice either. It is still somewhat fragile and requires a lot of annoying grinding-down work. The last choice was always there and I'm sure a lot of people have thought of it and dismissed it as crazy.

Epoxy putty.

At first thought, it seems absurd. Epoxy putty will create very uneven spacers and be even worse than tape, right?

I tried it out anyway because I was desperate for a good solution and low and behold, I got my first perfectly sealing pump! You need to make every minute with the putty count as you shape it. Let the edges of the putty go onto the O-ring slightly, but be absolutely sure the putty never extends above the O-ring. You will have to cut down the putty stick to a very small length so be careful. If you get the edges of the O-ring right, you got a good spacer. Make sure everything is as even as possible.

In the end, I still couldn't get the spacer to fit perfectly, but it worked after I took out a dremel and grinded it down. Here's a thousand words on the matter:


Yes, I'm still using tape as the top spacer as this is mostly experimental, but I'll take care of it later. You can see that the tape has been push out pretty far, but it has been stopped by the blob of putty at the end. Since the 1/2" aluminum rod is hollow, I needed the putty to keep that area sealed, but I ended up using excessive amounts last time.

I may end up keeping the tape there, while adding a little bit more putty at the end to keep the tape held in place. This makes the assembly less permanent.

Lastly, I only got one test off of this. Chances are that this may not even be a reliable solution; it could break down in months just like any other pump I made. However, I still consider this an important success since I never had a pump seal half as well as I just did.

I hope this helps people build their pumps. I'm very surprised that few people are posting about issues with them, so either they're not having problems with their pumps, deal with the leaks, or simply aren't building APH/CPH's.

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Re: Pumps

Post by Killi101 » Sun Jun 20, 2010 9:24 am

Ive had problems with my pump which i made...
to make it i used:

40cm 15mm copper pipe
X2 end caps
a rubber washer of some kind...
5mm screw

Problem for me was i had to make a seal for a 22mm pipe that would fit on the 15mm pipe, didnt happen so i put an end cap on one end, welded it, then i drilled a 4.5mm hole in the other endcap, placed the washer along the hole, screwed it in, placed mini washer and nut on other end. i had to carefully weld the second endcap with the rubber washer attached on to the pipe. from there i had to sand the rubber washer until it fitted into the 22mm pipe, it gave a VERY TIGHT SEAL! you had to lube it every time you wanted to use it otherwise it comes out, which acctually happened when i didnt lube it. it took a while to fix but it works very effectively heres a pic:


this is for all those who need to build their pump from copper pipe, heres a solution
dont like drinking much
like to throw it at people

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Re: Pumps

Post by chaosfox97 » Sun Jul 18, 2010 1:31 am

What if you had a 3/4 pump valve, what would you get then?