Description Everbuild P20 Plumbers Flux Soldering Paste is a soft paste which is applied to joint areas prior to soldering. P20 Plumbers Flux Soldering Paste is suitable for use with most metal types and can be used on both and cold water pipes. P20 Plumbers Flux soldering Paste also benefits from being self-cleaning and as well as the fact it can be used with potable water.