Before you get into pumping, you'd better know the risks and how to avoid them.

Nearly all potential problems stem from applying too much pressure for too long. Here's the bad news. I've made all the mistakes and experienced the "minor problems" myself (see the photo of my water blister at the right). Fortunately, I have not had to deal with the major ones.

If you develop any of the minor problems other than petechia, stop pumping for as long as it takes to return to normal, plus an extra 5 days to be sure you've healed. Then start up again, slow and easy. For petechia, take a day or two off.

If you develop any of the major problems, stop pumping and see a doctor right away.

If you get a piercing, stop pumping for several weeks to allow complete healing. Also, it usually works better to leave your jewelry on while you pump.

Darkening of the shaft - caused by buildup of minerals drawn into the skin with other fluids when you pump. Eventually they will flush out.

You can lessen the buildup by improving circulation, either by milking the tube or by taking a break and milking your dick.

Best way to prevent darkening is to drink plenty of water before you pump, and use lower pressure so you're not forcing fluid into the cock skin so fast. When you pump slower, more volume goes into the core, and the fluids have more time for minerals to get filtered out.

Petechia or "pin-cushion spots" - tiny blood blisters or bruises caused by burst capillaries in the skin. They can heal in a couple days, or spread and last for weeks or even months. The glans is especially susceptible, as the tissue there does not stretch easily. I've had repeated bouts of petechia on my glans.

The best way to avoid petechia is to control your pressure according to your sensations - if you feel pinpricks or localized pain in the glans, immediately back off the pressure and stay below that level until your cock is really stretching out. Warming up the cock, and pumping in warm water also help.

Once you have petechia, stop pumping for a couple days. If it doesn't go away, I have found the best cure is actually to start pumping again. Pump moderately for 15 - 30 minutes every day, light pressure, no pain. Before and after the pump, coat your glans with sticky hand creme like George's or Noxema. These are more healing than lube or light cremes.

George's cream can also help prevent petechia. Slather it over your glans before pumping. The cream helps the tissue expand easier, but also seals the skin against the vacuum pressure.

Bruises - caused by too much pressure bursting blood vessels in your skin; take about 5 days to heal.

Water blisters - caused by too much pressure on your glans (cock head); may also be caused by using water that's too hot when pumping wet; take about 5 days to heal.

Donut - excessive swelling of the foreskin - caused by prolonged pressure overinflating the elastic foreskin tissue; some guys want a donut to stretch their foreskin; returns to normal after 2 - 24 hours; you can reduce it by massaging the penis between pumping sets.

Ugly mis-shapen dick - sometimes as you deflate after pumping, your dick will look rather shrivelled or twisted; this effect goes away after a few hours; having an erection along the way helps.

Loss of erectile fulness, difficulty getting or sustaining an erection; caused by straining the tissues of the corpus cavernosa (your "hardening tubes") or by damage to the blood vessel valves that lock blood into the erect cock; takes 1 - 3 days to return to normal.

Peyronie's disease - long-term erectile dysfunction; caused by damage to the blood vessel valves; if you suspect this, see a urologist immediately.

Clots or other lumps in penile tissue; caused by repeated, chronic bruising; may disappear over time.

Be patient and take it easy! Pumping takes time, and that time can be very enjoyable, so why push it?

Watch your vacuum pressure! Follow the pressure guide further below. In general, use less pressure than your testosterone-fuelled brain wants to. The pressure should feel light during most of your session, and comfortably snug toward the end.

Build up gradually. Pay attention to the results you get and only slowly increase the length of your sessions or the level of pressure. You should pump for no more than 30 minutes during the first month, and no more than 1 hour during the first 6 months.

Pump regularly. This way you won't be so tempted to go overboard, and you'll get better at tracking your results and identifying your best techniques.