Menstrual cups are a popular, environmentally conscious choice for period management. They function by creating a seal against the vaginal walls to collect fluid, allowing activities like swimming without leakage worry. However, users often discover the cup has collected pool or ocean water upon removal. This phenomenon occurs because a combination of anatomical factors and external forces can compromise the cup’s seal. This article explains the physics behind water entry and offers practical steps to keep your cup secure while swimming.
Understanding the Seal and Pressure Dynamics
A menstrual cup relies on a vacuum seal, or suction, formed between the cup’s rim and the vaginal walls to remain in place and prevent leaks. Since the vaginal canal is not completely airtight, this imperfect seal allows the external environment to influence the cup’s contents. When submerged, the surrounding water exerts hydrostatic pressure, which increases with depth and movement.
Swimming motions, diving, or quick movements cause abrupt changes in this external pressure against the lower body. This force can momentarily press against the pelvic floor and vaginal entrance. If the cup’s vacuum seal is compromised—due to slight shifting, material softness, or a minor fold in the rim—this external water pressure can force water past the seal and into the cup.
Some cups feature small ventilation holes near the rim, necessary to help break the seal for removal. A temporary disruption of the seal can create a pressure differential, potentially drawing a tiny amount of water through these openings.
Assessing Health and Hygiene Risks from Water Exposure
Discovering water inside your cup post-swim raises hygiene questions, as pool and ocean water contain elements foreign to the sensitive vaginal environment. Pool water contains chlorine, which can irritate the delicate mucous membranes. Ocean water contains salt and microorganisms that may disrupt the natural balance of vaginal flora.
The vagina maintains a slightly acidic pH (3.8 to 4.5) that protects against bacterial and yeast overgrowth. Introducing external water can temporarily raise the vaginal pH, increasing susceptibility to irritation, bacterial vaginosis, or yeast infections. The cup acts as a barrier, preventing prolonged contact between contaminants and the vaginal walls.
To mitigate potential risk, immediate post-swim care is necessary if water has entered the cup. Upon exiting the water, empty the cup immediately, discarding the mixture of menstrual fluid and external water. Thoroughly rinse the cup with clean water and reinsert it, or clean it with mild, unscented soap and warm water before reinsertion. This quick action minimizes the duration foreign substances are held near the vaginal opening, helping the body restore the proper pH balance.
Actionable Steps to Prevent Water Entry While Swimming
The most effective way to prevent water entry is to establish the best possible seal before swimming.
Ensuring Proper Insertion
Empty the cup just before you plan to swim, as a full cup creates internal pressure that makes the seal more vulnerable to external forces. Practicing different folding techniques and confirming the cup has fully opened after insertion can significantly improve the seal’s integrity. After inserting the cup, gently run a clean finger around the base to check for any indentations or folds in the silicone material. A perfectly round base indicates the cup has fully opened and is forming a tight seal against the vaginal walls. You can also lightly tug on the stem; a correctly sealed cup should resist being pulled down due to the suction.
Choosing the Right Cup and Activity
For users who swim regularly, choosing a firmer cup model may be beneficial. A stiffer rim is less likely to collapse or shift under the pressure of movement and water resistance. Limiting high-impact activities like aggressive diving or intense flip turns can also reduce the likelihood of the seal breaking. Ensuring a tight vacuum seal and emptying the cup immediately before getting in the water maximizes the cup’s ability to withstand the dynamic pressures of swimming.