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You might try using vinigar to try and break up the suds. If that doesn't work, "Pet Doctor" (the carpet cleaning products sold in grocery stores) has a "anti-foam" fluid that you use in the machine to keep the suds from building up. This stuff does work with the carpet shampoo which does foam up quite a bit without this stuff. It might be worth it to pick up a bottle and try running your machine with it in there.