Hello, need to run pvc pipe from the house to the new barn that is 350' away. Requesting your advice as to which (?? PVC40 ??) and what diameter to get pressure way out there. My rescue horses are both a blessing and a learning experience! Sure do appreciate your help. Thank you.

I would think it would be faster and cheaper to use black poly, like they use for wells.

my friend from CT is correct..
i would think 1 1/2 inch black poly pipe would do the job.
you probably will have to buy a 500 foot roll but there will only be connection at the beginning and at the end.

If you are just using horse waterers, then 1" would be adequate.

Thank you for your responses. The water needs to be safe for people to drink, too, and I've read that black poly may not be, plus it's not as long-lasting as PVC -- or is that incorrect? This will be buried 24" deep along with the electric line going to the barn. I really don't want to have to dig it up and repair it in a few years.
Thank you for the 1" response. You've surprised me with the "black poly" responses. Will the black poly last as long as the PVC? I'm in South Florida. Thanks.

polyethylene pipe has been used for wells for decades.
just do an internet search for "is polyethylene pipe safe for drinking water".
as hj suggested.. if you are just going to have a hose faucet for horse drinking water than 1 inch is sufficient.
but if you think that sometime in the future you may want to install some plumbing then go for the bigger size now.
the pipe might cost more but the labor to install it will be the same.

The pressure must be accounted for when sizing pipes. If the pressure is over 80 PSI, consider Schedule 80 PVC.