Big pipes make it easier for the flow of water to happen without meeting resistance. The slower the water moves, the better.

Big pipes are more important on the suction side.

I am assuming there is a booster powered pool sweep also, even though it's not been mentioned. These are always 1-1/2 inch piping.

When in circulation mode, the water is usually moving slower. As such, the 2" and 1.5" plumbing is usually fine. Eyeball return fittings, if used are usually smaller, either 3/4" or 1" in size.

The 2.5" suction on the spa generally allows for water to move faster and thus, provide added pressure. I am assuming you have 8 jets and not 6.

You mentioned two WFs. Both are attached to the slide?

Scott

Impossible question to answer without knowing how long the pipe runs are and the volume requirements for your water features, slide and spa jets. Your pool builder probably knows though.

The Pentair Intelliflo VS3050 variable 4 speed recommends 3" suction line plumbing to maximize efficiency. Not sure which variable speed you have, but 2-1/2" is better than many PBs use

Alas, pipe size gets reduced at the pump to two inches and all the equipment such as the filter, heater, salt cell are 2" also.

While 3" pipes certainly reduce the flow's friction and thus, the head loss induced traveling from the pad to the pool, the fact that the motor speed is normally run slower makes the 2.5 suction lines and 2" returns palatable. The XF style version, once it makes it's arrival, will make this an entirely moot issue as it will have the larger pipe size connections.

Hopefully all the other gear will get pipe size upgrades too. I normally hate scuttlebutt but I hear one of the main measures the commercial guys use to differentiate from the residential gear is pipe size. The way I see it, if Zodiac/Jandy can sort it out, so will Pentair.

Pool designs, hydraulically speaking, are becoming more green when it comes to energy usage and this is the way of the future. Slower moving water takes less energy and bigger pipes helps this immensely.

Scott