What position should the 3-way valve to the skimmer and main drain be on?

This is a frequent question we receive – Should the 3-way valve on my inground pool be on the skimmer, the main drain, or a partial opening of the two of them? 

50/50 is the quick answer, however, there are reasons for having it be different than a 50/50 split between them. Every pool is different.

Does your swimming pool receive a lot of leaves or other floating debris?

More suction may be needed at the skimmer than the main drain to effectively remove the floating debris from the surface.  Therefore, you would want more of a skimmer opening than a main drain, about a 70/30 split – skimmer/main drain.

Is the majority of the debris on the bottom of the pool?

However, if more debris or dirt is found at the bottom of the pool then more suction at the main drain may be required. This time the 70/30 split – main drain/skimmer.

Are you trying to prime the pump?

If you are priming the pump, you should put it 100% on either side rather than a split between them.

How is your water level?

If your water level is low, put the valve all the way on main drain until the pool level is back to normal.

Are you trying to vacuum the pool?

Do you happen to use a manual vacuum or a side suction vacuum?  You will want to put the valve on 100% skimmer while you are vacuuming the pool.  The vacuum connects directly through the skimmer. Without it being set at 100% on skimmer you risk losing that suction you need to complete the vacuuming.  Once you are done the vacuuming, you should put the valve back to the position it was previously located.

If you are unsure what works best for your system, feel free to contact your pool professional for advice. If they are familiar with your pool set up they may be able to help you determine what the best 3-way valve position is for your pool.