Changing my resin so quickly.

[spruce]

Seems very confusing for newbies when the equipment tells you to do one thing and anyone who uses it says another. Thanks for trying to explain chaps. I’ve tried filling to the line but normally just brim it. Only difference I’ve ever found is the fuller the vessel the longer it lasts (not because the resin lasts longer, you just put more in lol). Never had any problem with water circulating when it was just 2/3 full, worked exactly the same. I’ve also never had a problem with channeling myself but I have mine van mounted so it does run super slow and with my driving skillz the resin stays as well shaken as 007’s Martini. 
 

Don’t know if the Op sorted the problem but I still think having a vessel 2/3 full wasn’t it. ?

Unfortunately we live in a world of mass production. Not much is manufactured for a specific purpose any more. Much is due to cost which is driven by competition and the price the consumer is prepared to pay.

Our industry has many examples of components that are designed for different markets such as hose coupling from the garden industry and air line industries. Our batteries and in vehicle charging equipment started off in the leisure and marine industries.

Some sellers actually haven't a clue what they are selling and often they don't care to know. Ask a question and they just shrug their shoulders.

How many window cleaners have bought new systems from suppliers and then come on here asking how to use it as they didn't receive any instructions. This is why we often refer people to @doug atkinsonbecause we know that he will supply items that are fit for purpose with backup. Sadly, people ask his advice then troll the internet looking for the cheapest price.

 

[Pjj]

As Dough has explained it should be filled to the shoulder otherwise the water doesn’t  go through the resin properly it will channel causing untreated water to enter the tank thus giving a TDS reading  

 

[Will Eves]

@spruce You’ve probably hit the nail on the head there. I have a DI from 12 years ago and even though the label is long gone it didn’t have a “don’t fill above” line whereas one I bought 2 years ago does. Same brand, identical inside just a different sticker. Back in the day I guess they were aimed more at window cleaners but now they’re marketing them for more uses too. 
Mine are Spectrum ones and have always come from one of the main window cleaning sites rather than eBay or anything. 
Good thing for people to know I suppose, glad I asked. I bet plenty of people have filled it to that exact line hundreds of times and never asked themselves why lol. The fuller you fill it the less often you have to refill it, thankfully.