Okay, a couple of days ago I thought I'd try and make a new pump seal for my CPS 1000, as the stock one seemed a bit stiff. I'd done this several times before with other guns with very good results, so I thought I wouldn't have any problems. Anyway, the original seal wouldn't come off, so I ended up crushing it in a vice to get it off (didn't think I'd need it again). However, now I wish I hadn't; no matter what size o-ring I put on the pump, I cannot get a good seal. Even larger ones that are almost too big to fit inside the pump shaft still leak everywhere. So, any advice on what I can do to fix this?

Here's a pic so you can see what I've done so far. You can just see the 2 o-rings, held in place with electrical tape on the sides:

Try putting a layer or two of electrical tape under the O rings. This makes them a little larger.

Thanks, but I already tried that as well!

As I said, even when the o-ring is sufficiently large that it almost doesn't fit at all, it still leaks quite a lot. This is what puzzles me, as with the larger o-rings the pump becomes VERY difficult (yes I have lubricated the o-rings) indicating that they are a little too large and therefore should seal very well, yet it still manages to leak everywhere.

The seal created by o-rings is much much smaller than the seal of a normal production Super Soaker because the surface area of the o-reings that is actually making the seal is smaller than the stock seal. However, it is not as easy as just using lots of electrical tape. Make sure the pump is clean inside as dirt or other particles can obstruct the pump flow (may sound elementary, but it can add scratches to the plastic that obstruct the seal. Try seal a larger lateral portion of the pump, and use enough tape so that it is almost flush with the top of the o-rings. Also be careful not touse too much lubrication. I've heard some types slowly eat rubber.

Good luck and update us on progress.

Try using a different material for the pump shaft such as an aluminum rod. It would be a little harder to get the pump handle back on because you'd have to drill holes in the metal rod, but that wouldn't be impossible. It wouldn't hurt either because at worst, you won't use the metal rod.

It looks to me that you have used 2 o rings and they're spread apart. What I would do is get a few more. Maybe 4-5 in total and put themm all next to each other. THis has worked for me before.

Edit: You also may want to lube up the o rings before you put them in the tube.

Thanks for your comments. I have tried multiple o-rings right next to each other, but for some reason the 2nd o-ring refuses to go in. It just bunches up. That's why I tried seperating them with electrical tape. So it will be quite difficult to have 4-5 o-rings on there without making the pump ridiculously short with all the electrical tape seperating them.

I can't understand why on the other guns I've done this to (CPS 2700, SC500, CPS 1500 and my homemade) all only needed a single o-ring with electrical tape on the side to get a perfect seal.

Hmm, this may require more drastic methods, but I'm sure you'd like to avoid replacing the entire pump. A stock pump is without a doubt more comfortable than a homemade pump/grip. Try using slightly smaller o-rings and more of them. Then you can put them together without them bunching up, and perhaps get a better seal. Remember not to rely on lubrication too much. If you do, the pump is bound to leak every use.

Well, as Doom said, I could still use the original pump handle with a new pump shaft after drilling a couple of holes. Anyway, I'll keep at it, and try everyone's ideas and let you guys know how it goes.

Just tightly wrap electrical tape in one spot, put the pump in the gun every now and then to check for how it fits, and eventually it will fit perfectly. Two or three of my guns had pump problems, and this quick fix made them better than new, with perfect seals. B)

I finally figured out what the problem was, and it had nothing to do with the o-rings I was using at all! After I'd crushed the end of the pump with the vice, the plastic that attaches the original seal had broken off as well (you can see this in the pic in my first post). There is a hole in the middle of the pump at the end where the screw for attaching the seal goes. That hole was now exposed...so as I pumped, water was travelling into the hole, right through the hollow pump shaft, and leaking out the other end at the handle!

I noticed this after I took off the pump cap, and noticed that no water was leaking out of the pump shaft. So now all I have to do is seal the hole, and the problem is fixed. Will update later on my progress.

Well I sealed the hole at the end, waited for the epoxy to dry, then tried the pump once again. And it still leaked! Then I had another look at the pump. If you look closely in the first picture, you can see a crack on the yellow part beside the o-rings. That's where the water was getting in! So I put a very thin layer of epoxy on that, and finally the gun sealed.

So a happy ending after all, now my 1000 is ready for when summer rolls around later this year.

Congratulations on the successful and (relatively) clean repair. The CPS 1000 is a fantastic water gun, and I hoep you have a lot of fun this summer!

If you have any wars, update us, and as always pics are welcome!

Soak On