Surface water treated or purchased by HWD from MWD undergoes multiple stages of treatment including filtration, which is critical for the removal of these organisms. HWD and MWD monitor their source water and treated finished water on a monthly basis for both Cryptosporidium and Giardia. To date, no Giardia have been detected in finished water.

There is very low risk, if any, to the general public of contracting either disease from drinking water served by HWD. State health officials, however, recommend that persons with severely compromised immune systems, especially persons with AIDS, should consult a physician about preventing infection from all potential sources. If they want to further reduce their potential risk, they may want to take special precautions, including boiling water for one minute before drinking it.