In the near future, I'm going to be installing a large sump basin (50 to 70 gallons or so) in the crawlspace with two new pumps that are more efficient and will kick out even more water with little noise. Each pump will have its own pipe with a roughly 7' initial head, then both will run about 5 feet horizontal and go out of the crawlspace to the outside, make a 90 degree turn and somewhere around that area just outside of the house it will split into a single PVC pipe to continue the 20-25ft run out into the back yard. The pumps can handle it and are designed for up to a 25ft head with no problem. I'm doing this joining of the pipes outside because if the two pipes joined a single larger pipe inside of the crawlspace and something happened to the larger main pipe, that would be a big failure. However, with two separate pipes going outside, there is a backup and it would at least get the water outside of the house even if the split to the large pipe came loose outside of the house. I just like to plan ahead of time. I talked to the guy at the place where I'll be buying the pumps. He told me, "I would suggest that you tie those two discharge pipes to a minimum 2-1/2" or even 3" PVC pipe for maximum performance. As long as the horizontal pumping distance is not extreme, you will be fine." Is it really that simple - doubling the pipe size to whatever the main pipe is to be? My research hasn't been coming up with that. One will be primary and one for backup. Each pump can kick out about 3,330GPH, or roughly 55GPM. In the rare crazy rain event where both need to come on and 110GPM is going through one pipe, I want to make sure it is big enough. However, apparently a pipe that is too big has the opposite effect - losing pressure to push the water out fast enough and with enough force. Suggestions? I have done Google searches and such, but there always seems to be conflicting information. One place says x thousands of gallons should flow through x size pipe, and then another place says something totally different. I want maximum flow rate for each pump without losing the pressure. I really need to angle the entire horizontal pipe run (the part that runs along the ground) a little bit somehow, so that nothing freezes in the pipe during the winter discharges.