Before you call a repairman.
The first thing to do is to calmly go to your alarm box and switch it to silent, a red lite will remain on until this problem is fixed. Next go to your circuit breaker panel and check for a blown breaker. If the breaker for your system is off, turn it back on and wait a few minutes for the alarm to go off. If the alarm light goes off, turn the horn back on and keep close watch of the system for a few days.. Some systems with an outlet filter will have a warning alarm to indicate when the filter is getting clogged up. If your alarm sounds intermittently or only when you use moderate amounts of water (doing laundry, emptying a bathtub, etc.), this could be an indication of a clogged filter. Please refer to the filter page of this website for tips on filter cleaning. If your alarm lite remains on you should call your service provider. Keep in mind systems with pumps will have a reserve capacity, equal to about one days average use, to allow the repairman time to get to your system
After you call a repairman.
Have any questions you may have about your system and it's operation ready and ask your service provider. Most will be happy to give you a walk around and explain the various parts of your particuler system as well as tips on how best to keep the system trouble free. If you or your service provider have not already done so, reset your alarm back to the audible setting, some automatically reset, but check to be sure.