Rubbery membrane on bottom of "T" exhaust

[jslinger]

After last spring I attempted to clean the exhaust of my pellet stove. I had only used 1/2 ton, but thought I might as well do it anyway.
My exhaust goes up and out, so both 90* are inside the house.
I bought a 3" diameter brush, but couldn't get it past the 90* elbow. Any tips on how to get it all the way through would be appreciated.
I just pulled the cap off the bottom of the exhaust (where I assume the soot is supposed to collect after running a brush through. It was completely clean. I used a flashlight and mirror to look up inside the exhaust and there is a soft rubber membrane over the bottom, so the soot can't drop out. Is this supposed to be there? Or should I attempt to peel it off?
Thanks for the help.

 

[Bioburner]

Post a pick if possible. Leftover from install-glove etc?

 

[urkiddin]

I changed my 90 deg ell to 2- 45 deg ells so I could get the brush thru. worked for me but it did move the stove out a little more.

 

[smwilliamson]

that's a silicone gasket

 

[TheMightyMoe]

Lint eater will make 90*s with drill spinning it, I spin to get past 90* then hand brush.

 

[jslinger]

Lint eater will make 90*s with drill spinning it, I spin to get past 90* then hand brush.

It seems like the brush is 4" diameter. Is it flexible enough to fit into a 3" pipe?

 

[smwilliamson]

It seems like the brush is 4" diameter. Is it flexible enough to fit into a 3" pipe?

Yup