With the mitigated fast can you drink water before mass or are you constrained to 1 hour before communion? I know alcohol is 3 hours and non-alcohol is 1 hour but what about water? I know water is not alcohol but I saw conflicting information on this.

As Ladislaus wrote, taking water does not break the Eucharistic fast.    Drinking water before Holy Communion became permissible in 1953 with Pope Pius XII’s apostolic constitution Christus Dominus.  There were other relaxations of the fast for those in particular circuмstances, but the fast from solid food and beverages other than water from midnight continued.  The three hour fast from solid food and alcohol and one hour from beverages other than water came into effect with Sacram Communionem in 1957.  These changes were in conjunction with permitting Mass to be celebrated in the afternoon and early evening.  Previously Mass was only celebrated between dawn and noon, except for the Christmas Mass at midnight, and a few other special circuмstances by indult.

I recall in First Communion catechism class in 1957 learning that in the “old days” people wouldn’t brush their teeth or even rinse their mouth for fear of accidentally swallowing a drop of water and not being able to go to Holy Communion.  I am thinking priests are grateful that people now will brush their teeth and tongue and rinse their mouths before coming to the communion rail.

If I plan to take Holy Communion I fast from solid food from midnight (or noon if I’m going to an evening Mass, which is sometimes necessary because of work) as Pope XII encouraged everyone to do if they are able.  I am thankful for the permitting of water and other beverages.  The 90 minute drive I’ll make tomorrow for a High Mass of Christmas Day would be a challenge if I didn’t have a cup or two of coffee.

A couple of references:
https://fatima.org/news-views/what-is-the-eucharistic-fast (there is a reference to the 1983 Code of Canon Law, which some find offensive).

https://en.wikipedia.org/wiki/Liturgical_reforms_of_Pope_Pius_XII

On the first sentence, not just for the priest's sake. If we're allowed post Pius XII, it seems a more fitting preparation to receive Our Lord.

On the last two sentences, back when folks could still walk to a true Mass or, for longer distances, harness a donkey or horse to pull the cart reliably, the midnight fast from water was one thing. But driving at foggy daybreak while looking around for deer and black ice... not the prudent thing to do while dehydrated especially as one gets older.

I agree.  Because that’s what I’ll be doing, only for three hours and add possible moose into the equation!  Deers’ eyes reflect in car headlights, whereas the moose’s eyes do not.  

Also moose (meese?) are a whole lot bigger. Drive safe and pack a thermos of coffee, or tea, or even plain hot water!

No such thing as meese!  The singular and plural are the same.  Yes, they’re a whole lot bigger than deer.  I knew a lady many years ago who hit a cow moose and totaled her car.  She had whiplash and cuts and bruises, the days before shoulder harnesses and airbags, only a lap belt which she fortunately had on.  The car, a Chevy Nova, was a total loss.  The state police who responded had to put the moose down.  

Maybe this question is stupid or unnecessary. Does one need to hold Eucharistic fast (3 hours or more) if he/she would watch Mass on livestream and receieve Our Lord only in spiritual Communion?

No fast is required for a spiritual communion. 

Thank you for this simple and clear answer. Did pope Pius XII reduced fasting to 3 hours before Mass because of people working and assisting at Mass in the afternoon?
My only chance to assist at (or attend?) at TLM is usually at 18:00, at SSPX chapel.
If I recall, pope Pius XII. encouraged to hold midnight fast as much as possible.

I do believe that the 3-hour fast was tied to permission to have afternoon Masses, since if you attend a 7 PM Mass, for instance, fasting from midnight would not be doable for most people ... although the 3-hour fast was not limited to afternoon Masses.  You could eat at 5:30 AM and then receive Holy Communion at the 9AM Mass, for instance.

Thank you Ladislaus for further explanation of this question.

The docuмent that specifically changed the time frame for the Mass speaks of the technological advances in transportation.  Prior to such advances, priests would have to travel long distances over a period of days to say Mass in locations distant from parish churches where priests live.  The ability to travel longer distances by train and car make it possible for priests to travel these distances in much shorter time so that the priest can say Mass at his home parish and then travel to a more remote community of Catholics to say Mass for Catholics who would be otherwise unable to attend Mass frequently.  The Holy Father recognized that such travel while fasting could often be unsafe for the priests.  It was my understanding that the permission to say Mass after noon came later, but I may be mistaken on this.

I'm reminded here of Fr Courtney Krier in Las Vegas, who at one time drove all the way to Needles, California after having said at least two Masses on Sunday, all this, I assume, without having eaten.  I suppose some people's bodies could get used to such a thing --- mine couldn't for health reasons --- but traditional practices didn't presuppose Mass after noon.