possible filter problem

[drozdjeniferj]

After dumping large amounts of shock, buying a bigger sand filter, putting "green to clean" to get rid of Swamp in our pool the algae finally sank to bottom. We started vacuuming on waste to just get rid of the algae instead of filtering it. When putting filter on waste position, some of the algae was coming back into the pool through the jet! I did not think water was supposed to be coming back into pool on waste position. Is our brand new filter not working properly?

[Watermom]

When putting filter on waste position, some of the algae was coming back into the pool through the jet! I did not think water was supposed to be coming back into pool on waste position. Is our brand new filter not working properly?

Yep! It definitely should not do that.

[CarlD]

The very first thing to check is your multivalve on top (or side) of the filter.
First logical answer is either the spider gasket has failed or is installed wrong. Replace.
Second logical answer: One of the walls of the multivalve chambers is damaged and water is leaking through. You'll have to replace it.
After that it gets too tough to guess.