Here is a manifold system, albeit a gas manifold, but the theory is the same. Flow is from right to left. The manifold starts after the regulator (or pump in your case). This would be considered a 1" manifold. The first tee is 1" x 3/4" and goes to the furnace. The second tee is 1" x 3/4" again and goes to the range. 3rd tee is 1" x 3/4" x 1/2" with the 1/2" going to the water heater. The end of the manifold on the left carries on in 3/4" to the BBQ and fire pit on the deck. Just out of frame on the left is a 3/4" union and as you can see there is a 1" union just before the reg. The theory is the same for plumbing just utilizing different materials.
