Depends on type of overflow plumbing.................

Two options:

1. Replace the ENTIRE intake standpipe in the overflows with a Durso type Standpipe. Google search (Durso Standpipe) on this, but here is one link with a pic...

Durso Standpipes Portal > Home

2. I have a floating type sponge/buoy setup (hard to explain sorry) where I was able to insert a 2" extension piece of 1" PVC (using a collar adaptor) to lengthen the existing standpipe. Length of extension is of course based on size of your overflows.

As stated, I have plenty of posts recently around this, so search for my username threads...

Remember that more water in the overflows, may mean more in the sump, so be careful it doesn't spill over.....

Good luck.