HELP! Deep end strainer losing suction

[freeflynick]

Hello!
I have an in-ground pool and hot tub setup. I have noticed recently that the deep end skimmer is sucking a fraction of the volume that the shallow end skimmer takes in. I noticed this first when vacuuming the pool - I usually "choke back" whichever skimmer I am not hooked into with the hose to provide greater suction to the hose, and when I went to the deep end I noticed very little suction, even with the shallow end skimmer valve closed completely.
It is also clearly seen when looking into the top of the skimmer basket housing - when I close the deep end skimmer there is still a strong flow from the shallow end but when I open the deep end and close the shallow end, the flow slows significantly.
I cannot see any obvious obstructions in the skimmer.
Any advice on what could be causing this or what troubleshooting I can do to identify a potential problem?
Thanks!!
Nick

 

[Richard320]

When you say "strainer" do you mean skimmer?

When you connect the vacuum, are you plugging straight into the port or are you using a vacuum plate?

Is there a main drain at the bottom of the pool and is it plumbed to the slow skimmer? If there is, and it's open, you won't see much flow in the skimmer and get hardly any suction to a vacuum plate. It's easier to draw water through a short pipe than a long narrow twisted hose, so it will pull from the drain not the vacuum.

 

[freeflynick]

Yes - strainer = skimmer.....will edit post.
I plug the vacuum directly into the hole in the bottom of the skimmer basket housing.
There are two drains in the bottom of the pool and one (possible two, cannot recall) in the bottom of the hot tub. I don't know how they are plumbed into the system.

If the photo uploads (fingers crossed!) it shows the valves (from left to right): To Fountains, to pool jets, to deck Fountains (deck jets), To spa. From shallow skimmer, from deep end skimmer, from spa.
I don't touch the valve 2nd from left, which I am pretty sure goes to the pool jets.The two auto valves I assume are for switching from pool to spa "modes". That's about the extent of my knowledge!
Any advice given what I have shown here?

 

[Richard320]

Since you're plugging in directly to the port, I'd guess you have a clog in the underground pipe, a wad of leaves or pine needles. If you set the valves to draw totally from the restricted skimmer, then stuff a garden hose into the pipes from inside the pump strainer and flow water backwards, you may dislodge it. Seal it with a rag. It doesn't appear you have room to use a drain king as close as that threeway is to the pump intake.

 

[freeflynick]

I will give that a try - thanks!

 

[freeflynick]

Tried your recommendation but no joy.
Is there any risk in snaking the lines with a plumbing snake? Could it damage the valve seals?