Super Soaker Central

As I've said previously, in my experience piston pumpers can impress on the firing range, rivalling if not quite matching pressurised blasters. But on the battlefield, they're hard to aim precisely. (Especially considering that to get the best range from a piston pumper, I brace the rear of the gun against my shoulder, allowing me to apply more force; of course if you have more arm strength that won't be so necessary. But even holding it conventionally, aiming still lacks the precision a pressurised blaster can offer.)

If you can fight effectively with a piston pumper, then do so if you want. I can't, so I'll stick to pressurised blasters unless I have no choice or it's a non-serious water fight.

Most pumpers are very, very difficult to get to pressurized blaster range. The shot is short, unsubstantial, and you have to hold the blaster very precisely while pumping. Even if its possible to get a pumper to perform better than the average XP, it takes a lot of skill to develop that can better be spent to improving shots for conventional blasters, dodging, etc.

That said, piston pumpers are still useful. I've mentioned before that I use them for our Infection game, where the water weaponry is supposed to be very unbalanced by the nature of the game. By their very nature, they are intended only for casual wars (usually soakfests), and they serve a purpose for their niche. Of course, you could also have a serious war where everyone is equipped with only piston pumpers, but it's probably not as fun.

Homemade piston pumpers can eliminate some of the drawbacks. The really basic PVC Piston Pumper model hits the mid-50's and the shot can last for 1-3 seconds. You don't need to be particularly strong, but you do need to contract your power quickly and hold it. Just takes practice. However, it's still hard to aim the things, you can't keep them in drawn position for long if at all, and you need a water source to draw from. Piston pumpers are one of the most ideal river and pool guns because they can draw straight from the nozzle. I would choose one over most other types of guns in a war involving any kind of boat. Backpack feeds allow you to bypass the drawing problem, but a different type of homemade would work better in that situation.

Backpack/separate feeds for pistons result in lower performance since two check valves are needed, one of which will constrict flow when pushing out wards.

The Waterzooka seems to be ideal for piston pumpers as it uses hydraulics for better efficiency. That said, I'd still take a mounted (detachable) APH, perhaps powered by foot pumps, over a piston pumper, though a mounted piston pumper may also work well as its easier to channel more force into the shot.