Plastic Taste coming from the Tanks
Years ago, we were caught out and had to use a garden hose to fill our tanks. That plastic taste that is released from the garden hose stayed with us for several weeks.
Rule #1 - ALWAYS! use a food grade drinking water hose. Never a garden hose. Unfortunately, I have seen, in the some RV manufacturing factories, where they fill from a garden hose (and in one case even from a fire hose) to test the plumbing system of the newly built rig.
This will taint the tanks, pumps and plumbing and it is very hard to get rid of - Until now.
An old guy came up to my stand at the Perth Caravan Show one year, and told me that he had been in the industry for years, and that there was only one thing that will get the plastic taste out of the water tanks and pipes and that is - Cheap 'no brand' (Black & Gold / No Frills) red cordial!
I thought he was joking, but he was serious.
A short time later, we hired a camper trailer. It had the worst water taint I have ever tasted, so I thought I'd try this red cordial method.
I totally drained the tank and poured the 2L red cordial in using a funnel, and then filled the tanks up completely. (Be careful when putting the red cordial in - if it spills, make sure you wipe it off straight away, as it may stain light surfaces.) I then pumped water through the outlet/s until it was coming out red from the tap.
I did leave it sit overnight, however I don't know whether I needed to leave it that long or not. The next day, I drained the system and flushed it out with fresh water.
After re-filling, my kids drank the water- and they have been brought up only filtered water only!
So, for a few dollars, it's worth a go!
Please also take time to check your piping!
The 'plastic taste' problem could also be the tubing that connects the tank to the tap. If it's clear tubing, some of them break down after a few years and need to be replaced.
To test this, take some water from the tap. Then, disconnect the tube at the tank, and catch some water in a cup (directly from the tank, without going through any pipework after the tank). Taste test the tank water - if it taste's ok, then taste test the tap water. If it's not ok from the tap, then you know it's the tubing connecting the two.