Pool Pressure Drops about 5 PSI - when valve set to full Main Drain

[mas985]

Probably just indicates that the main drain line has more head loss than the skimmer which is not unusual at all. Probably a longer run and maybe smaller pipe.

You want most of the flow from the skimmer anyway because it removes debris from the surface. MDs don't do much at all.

[zooba72]

Thanks for the reply - both good points It would be a single pipe as opposed to two and it's definitely a longer run.