Reasonable scepticism about service plans
Is annual servicing really necessary?
Necessary is a strong word. What is true is that valley water is at the hard end of the national range, and the failures we get called to are overwhelmingly maintenance ones: bridged salt, silted injectors, wrong settings. An annual look is the cheap way to avoid those. Skipping it is a real choice, not a disaster.
Can I do this myself?
A good part of it, yes. Keeping salt topped up with the right type, breaking up bridges and watching the salt level drop between months tells you most of what you need. What is harder at home is observing a full regeneration cycle and judging resin condition.
What salt should I be using?
Follow your unit manual, because this varies by equipment and we are not going to override the manufacturer documentation for your specific model. What we will say generally: the wrong salt for your unit is a common cause of mush and bridging, so it is worth checking the manual once rather than buying on price.