Clay is so fine it won't settle fast enough to stay out of pumps and
pipes. I installed my sump pipes with as much slope towards the outlet
as possible so they empty faster after each pump cycle. If you could
raise up the pipe inside the house and as far from the outlet as possible
you could get a bit of flushing action that may help.
Unless you have a very small capacity pump or a lot of bends (more than
two or three) then bigger pump won't help.
You could try to install some geotextile fabric around the inside of the
sump to see if it helps. You need as much filter flow area as you can get
to minimize plugging of the fabric. Make an inside sump pail about an
inch or two smaller than the sump out of some sort of screen material -
plastic is best to avoid galvanic action with pump steel. Tightly wrap
fabric around screen, drop screen into sump and pump into screen. You
must use the felt type fabric, NOT the woven type.
If you really want to try a cheap and quick fix - wrap the pump with some
heavy plastic window screen material, the type recommended for cat and
dog resistance and then wrap the screen with the fabric. Shape is like a
big sack to get most flow area. Tie it up around the discharge pipe. Then
just pull the wrapped up pump once in a while to check for clay buildup
on fabric and rinse if needed.
The fabris has a very high flow capacity when it is clean but you may get
flooding of basement if it plugs up with clay so you need to monitor it
and either replace or clean when required. If pipe is left plugged then
there is a risk of flooding from the existing setup as well. Either way
maintenance is required. Pump would overheat and burnout if flow was
restricted either on inlet side or outlet side. Inlet restriction is
worse for pumps.
Most risk of plugging is with highest inflows to sump so check it after
major storms plus on a regular schedule.
There may be some good news in that the amount of clay may reduce with
time. The situation within the ground may stabilize and reduce the amount
of clay contribution. You should do all of the usual yard drainage
improvements to reduce the volume of water infiltrating to the sump. That
would speed up stabilization. You can expect clay to re-appear after
severe storms so check for plugging of filter after all bad storms even
after problem seems to have disappeared for a few years.
As a possible idea - is there a potential source for the clay other than
the obvious drain tiles? There could be a leaky water line causing the
clay content. Is the sump pump running when it shouldn't be? Or more
often then it should? Is it running during periods of dry weather when
you wouldn't expect any water in the drain tiles? Is there a check valve
on the pump or in the discharge line near the pump? If not the reverse
flush from the line when the pump stops could be flashing clay from the
sump pit or surrounding material. Is there a floor to the sump or is it
sitting on bare soil? I've seen several sumps made from just a piece of
pipe standing upright.
The amount of clay deposition you describe seems huge - is yard drainage
really poor? Ground should slope well away from house in all directions
and all roof spouts directed well away.