Well, he is wrong about what "home run" means, but just about everything else he says is reasonable. They way he did/proposes to do the returns is one of the standard ways it is done. Separate runs all the way back to the equipment pad is also done, though not nearly as often.
On the grotto, how important the pipe size is depends on the design flow rate of the jets and the distance from the equipment pad to the grotto. The maximum flow rate numbers in the manual have little bearing on reality. Larger pipe will get higher max flow rates, and the ratio between pipe sizes is about right, but the actual flow rates will be something else entirely that depends on all of the details of the plumbing.
Plumbing wise, the grotto is like a spa. It is very common to use 2 1/2" or 3" pipe on a spa, especially if the runs are longer (say more than 20 feet).
Anyway, the specific jets used determine the flow rate you are trying to achieve and the pipe size and length determines how much flow rate you are going to get. If the builder knows what they are doing, they will have already balanced that out, and there is nothing to be gained by increasing the pipe size. On the other hand, builders don't always do those calculations correctly, or sometimes at all. Still I'm included to believe that they will have thought about it, and thus that upgrading the pipe won't get you anything.
On the grotto, how important the pipe size is depends on the design flow rate of the jets and the distance from the equipment pad to the grotto. The maximum flow rate numbers in the manual have little bearing on reality. Larger pipe will get higher max flow rates, and the ratio between pipe sizes is about right, but the actual flow rates will be something else entirely that depends on all of the details of the plumbing.
Plumbing wise, the grotto is like a spa. It is very common to use 2 1/2" or 3" pipe on a spa, especially if the runs are longer (say more than 20 feet).
Anyway, the specific jets used determine the flow rate you are trying to achieve and the pipe size and length determines how much flow rate you are going to get. If the builder knows what they are doing, they will have already balanced that out, and there is nothing to be gained by increasing the pipe size. On the other hand, builders don't always do those calculations correctly, or sometimes at all. Still I'm included to believe that they will have thought about it, and thus that upgrading the pipe won't get you anything.
