Pumps as a penis enlargement method have been around for a long time and have even shown to be successful for some users. However when speaking about using penis pumps, you have to consider the issue of safety which is a huge concern when using such products.
Basically a penis pump works like this:
A tube is placed over your penis, and the pump process is started by either manual pumping action or electric (automatic) means. The air is removed from the tube causing your penis to temporary swell with increased blood. Most purveyors of penis pumps then recommend you to put a strap at the base of your penis to maintain your erection.
Some of the problems that can occur from using pumps include:
You run the risk of getting lymph blisters on the glands of your penis from the contraption that you’re putting over it.
You run the risk of bleeding from burst capillaries. Suddenly sucking a lot of blood into your penis can rupture some penile blood vessels.
You run the risk of temporary impotence as consequences of the aforementioned risk.
CONCLUSION: While some users have reported success with the penis pump, I strongly feel the potential serious risks far outweigh the minimal chance for sustained growth.