Most definitely avoid tank water around mouth, eyes etc; for reasons Duanes mentioned, and other horrror stories I've heard, nothing major but would rather avoid!
I was going comment on that myself. Why start the syphon with your mouth? I usually just fill up the hose with water from the sink to start syphon.A side note. You don't need to suck on the hose to siphon . Just push the hose or gravel vac up and down in the water a few times to get it started.
Why start the syphon with your mouth? I usually just fill up the hose with water from the sink to start syphon.