For years in the Coleman shampoo vacs I've used warsaw 32 to 1 carpet shampoo. 20 ounces of shampoo in a 5 gallon bucket seems to work well and is very inexpensive on a per use application. I quit buying bulk from Warsaw so I've been using other products from Jon Don. JON-Don is a janatorial company that sells a lot of cleaning formulas designed for residential and commercial carpet cleaning use. They are kind of the
Kleen Rite of the janitorial industry. Most carpet/upholstery shampoos seem to be just surfactant, some with fragrance. Presprays, spot removers and Heavy soil removers (traffic lane cleaners)usually add solvent and/or alkalinity. The theory behind residntial carpet cleaning seemed to be that it is soil on the surface of the carpet fiber, not embedded. and a mild cleaner will suffice. Greasy soils may require solvent and/or alkalinity
Just playing around I've been home brewing fragramatics formulas for a couple of years because of the high shipping costs of liquids. It seems like almost any foaming product will "work"(foam up). Based on a post by some residential carpet cleaners I mixed up some green apple fabuloso the other day and it foamed fine and smelled good. Some neutral products I've played with have started to slime up over time several months)in the fragramatics shampoo tank. I've started using Meguiars All purpose cleaner as a spot remover product at 12 ounces per gallon of water. This makes my cost of spot remover at roughly 2.00-2.50 per gallon. Meguiars APC is widely used by the detailing industry and is regarded as effective and generally safe for almost all vehicle surface: carpet, upholstery, vinyl, etc. I just checked with some ph strips yesterday and just one once of APC in a gallon of water actually foams a little and raises the PH of the solution to around 10, which should prevent long term slime buildup issues, so I'm going to start to add an ounce of it to my shampoo formulas. Don't know if that will kill the scent or not. If you like to keep things simple and don't care about scent you could use the APC at 2-4 ounces per gallon (less than 1.00 per gallon of mixed solution)as a shampoo and 8-12 ounces per gallon as a spot remover. In all honesty you could probably do the same with most SS presoak formulas