WHAT IS A SYSTEM "LEAK"?
When you pump, you remove air from the cylinder- lowering the inside pressure or creating a partial vacuum. This creates a differential in the inside/outside pressures, which wants to suck something into the cylinder to equalize the two pressures. Pumping takes advantage of this effect, using it to draw blood and fluid into the genitalia. As that happens, the enlargement of your body reduces the remaining airspace, which makes the level of vacuum will drop. This drop in vacuum level is normal, and is slow. It's not a leak!

Leaks are present when air is being drawn into the system by the existing vacuum when the system is closed. There are two categories of leaks, the first being one created by problems sealing the cylinder to your body, and the second being a mechanical fault in the system itself. We will deal with both, but first you have to find the leak- and that is what this article will tell you how to do.

HOW TO LEAK-TEST YOUR PUMP SYSTEM
Leaks might seem hard to locate, but they aren't. Water and the right process is all you need. To start testing, you will need to fill your cylinder partially with water. Enter the cylinder, and create a vacuum with your pump. Now, follow these steps:

1. Position yourself with the tube up and entry down, where water covers the body-cylinder seal area. If you have bubbles coming up at that time, you have a Seal Leak, or if your cylinder has any kind of joint at this end you could have a Joint Leak.
2. Position yourself with the entry up, and the opposite end of the cylinder covered with water. If you have bubbles there, you need to determine where they originate at:
   
   (A) Bubbles from the outside edge of the hose fitting indicate a Thread Leak.
   (B) Bubbles from the center opening of the hose fitting indicates an Exterior Leak.
   (C) Bubbles from the joint between the cap and the tube indicate a Joint Leak.

SEAL LEAKS:
The seal area usually leaks because of a poor surface match between your body and the cylinder rim. If by chance you are using a cylinder whose shape and yours don't match at all, you may need a different cylinder. Generally, the problem is hair- and the solution is to shave. It also helps to use a lubricant such as PumpToy's Glyde, which will help seal small areas around hair that can create airways.

If you are using a PumpToy's Precision Seal, you will have substantially fewer body-seal leak problems, and a much greater tolerance of hair.

THREAD LEAKS:
Leaks around the vacuum connector fitting are usually easy to fix. The method depends on the way the fitting seals to the tube. Some seal with some type of thread sealant, which might be teflon tape or a liquid applied to the thread when it is installed. Others are sealed by an O-ring located just under the hexagonal part of the fitting, and this is usually visible from the outside as a black rubber line. O-ring seals are the superior method.

First, check to see if the fitting is loose. O-ring fittings need to be only moderately hand tightened; they will leak if either TOO TIGHT or TOO LOOSE. Fittings sealed with teflon or other thread sealants need to be tighter. Just remember you are dealing with plastics, not metal, so don't get carried away. Most cylinders can be sealed with an O-ring; so some taped thread type can be converted. O-rings that will fit are available at any hardware store, as is Teflon thread tape.

Occasionally when such an area leaks, it's best to remove the fitting and clean the threads on both sides, as well as the O-ring. Note that fittings sealed with tape or thread sealants MUST have the sealant replaced anytime the fitting is disturbed. When you have an O-ring sealed fitting off, examine the O-ring carefully for any cuts or distortion. If it's damaged, replace it.

EXTERIOR LEAKS:
This means the leak is outside the cylinder itself. The leak is either in the line-side part of your coupling, the line itself or the vacuum pump. To test this, you need to pull a vacuum in the pump and line without it being connected to the cylinder. If your line-side coupling shuts itself off automatically, fine- if not, put your finger over the end.

If you can't retain a vacuum:

Put the coupler part underwater while pulling vac. If you see water start rising in the hose, your coupling leaks. The usual reason is deposit of some kind in the coupler, which can be removed by cleaning and replacing the O-ring if needed. If that does not fix the problem, you may need to replace the fitting. First, be sure that the leak is not coming from the barb connection between the hose and fitting- that occasionally happens when a hose ages or softens. If the leak is there, replace your hose.

If the leak does not show in the coupler-hose end, then it is in your vacuum pump or the connection of the hose to the vac pump. Repairs vary widely with the pump type. Some are easily rebuild-able, some are not. The best starting point is to clean your pump, as debris causes most leaks.

JOINT LEAKS:
If you have a joint leak, you have a structural failure of the tube assembly.

The repair options are:

(A) Contact your tube maker about repairs.

(B) Repair it yourself:

• Obtain some acrylic solvent cement, such as IPS Weld-on. This will be found only at industrial plastics distributors. This cement will damage acrylic surfaces instantly, do not allow it to contact any area except the repair area of the joint. This material can be thin as water or like light syrup depending on the dissolved solids content. It is available in several levels. For spot repairs you want a fairly thin cement. (For a full cap installation you would want a heavy one unless your are able to polish and mate your surfaces perfectly.) Apply it on the outside of the cylinder only; don't use very much. Allow to cure for several hours before use, then re-test to see if you have successfully sealed the leak.
  
  
• From your hardware store, get some clear siliconized acrylic-based caulking. (Note that straight silicones do not stick well to acrylics) This typically comes in caulking-gun tubes, (about $3) which requires a gun to apply- about another $5 if you don't already have one. In some stores you can find it in a small hand-squeeze tube. The small tubes are much more than you need. This material will not attack the plastic, and cleans off easily. Apply it over the leak area from the outside, pressing it into the joint with your fingers. When you have covered it well, take a damp cloth and wipe off any excess. This kind of repair works, but is visible and unattractive.

These steps should help you locate and repair any pumping leak you may encounter!