Coroutine being called multiple times from trigger.

Hi peeps :)

I'm running the code below. Basically, I want the coroutine to take -10 from currCharLvl. currCharLvl stores the current charge level of the character, and when full is set to 100. However, when I run the coroutine, the player is left with a currCharLvl of 0.

I'm suspecting that the coroutine is being called multiple times, but not sure how.

Any help is greatly appreciated :)

(using C#)

 public Collider2D zapAnimation;
 public GameObject spawnObject;
 public Animator oilPipeAnim;

 private bool isActive;

 public static float pipeDemand;


 void Start(){
     pipeDemand = 10f;
 }



 void OnTriggerEnter2D (Collider2D other) {

     Debug.Log(other + " collides with oil pipe"); 

     if ((other.gameObject.tag == "zapAnimation") && (ChargePoint.currCharLvl >= pipeDemand) && (zapAnimation.gameObject.activeInHierarchy == true)) { 

         StartCoroutine (PipeDie());

     }
 }

 public IEnumerator PipeDie(){

     ChargePoint.currCharLvl = (ChargePoint.currCharLvl - pipeDemand);

     yield return new WaitForSeconds (1f);

     oilPipeAnim.SetTrigger ("pipeburst");

     yield return new WaitForSeconds (2.20f);

     Destroy (spawnObject);
     Debug.Log ("Pipe healed!");
 }

}