Looking up the indredients ...
Its not really a product with the sole purpose of neutralizing what ever prespray u used to clean the upholstery or carpet , it is a cleaning product which maintains a low PH . The main reason to help prevent problems like browning .
The PH lowering component is citric acid ... so if u just want PH neutralizing solution on its own u could buy some citric acid powder on ebay and dilute it .
The cleaning ' detergent ' ingredients in the fiber & fabric rince are a couple of terpenes a wetting agent and a Disinfectant .
Use it as u use any other cleaning product ... although u could use it to rince and neutralize another high ph prespray u used by putting in your water tank .
* OK , so now i read it is sold as a neutralizing product .
( But it does have orange terepene like HDSL and a few other detergent components which could only be there to aid cleaning as distinct from just neutralizing)