iis there any danger to my house fixtures from shuting down the main water valve from a exstended vacation

If your name implies your location, then no problem. You may wish to set your ice maker to OFF so it won't keep trying to refill but other than that you are good to go. I travel a great deal and shut mine off almost every week for a week or a month at a time.

Iasked because las vegas Nevada has high content of stuff that's detramental to hot water heaters,usulay reducing to half of there life span.thank you

las vegas

Not familiar with your water but met a few of your other machine with bad luck. Shutting off the water should not make a change to the effect on things like you water heater or mixing valves.

Thank you-------------------las vegas

Shutting off your water when you go on vacation is the cheapest insurance you'll ever get. I live in Florida where many people leave in the summer months. A small leak can devastate your home or condo while you're gone. I know! I've seen it!
Have a great vacation. Tom