Help me Understand My Plumbing - The Third Jet?

[canadianeh]

I’m trying to understand the “third jet”

We bought this house two years ago.
There are 3 jets in the pool. One next to skimmer has always been off. I asked the pool company about it, they said its from an “old” system which doesn’t make sense to me.

I asked the previous house owner. He thinks it was for a vacuum. He said he never used it.

It’s attached to jandy valve with a small filter.

If I open it, the third jet works and does push out water. The other two jets have less power.

Is there reason or not to understand/work this jet?

From my understanding:

Water comes in from top skimmer/bottom skimmer through the pump, then into the filter, then into the heater, then back into the pool.

It seems opening this would have some water bypassing the filter?

Any thoughts to help me understand? I'm just wondering if I'm missing out on a third jet. It does look good when it runs.

Can you make sense of the pictures / video? I've attached a small video and picture of the pump.

Thank you!

Small video:

https://imgur.com/TDOc8zN

 

[mas985]

It looks like it has it's own cartridge filter so it could have been used for a pressure side cleaner but that is an odd way of plumbing that.

 

[canadianeh]

It is the one attached to the cartridge filter.

 

[1poolman1]

That is a Jandy "Energy Filter." It was used along with a Jandy RayVac, a non-booster pressure-side cleaner. If they worked, they worked well, right up until something went wrong, which was way too often. You can still find them for sale on occasionally ebay, but please, don't. They were so inexpensive that builders would give them away if you signed with them. Because there were so many of those made, and very dis-satisfied owners, the Polaris 360 was designed to take its place in the port that is fed by the Energy Filter.

Doesn't hurt to leave the valve in that position, but the filter will allow smaller debris through. Not likely enough to worry about, though.