Maintenance-free watercooling...

I'm building a new watercooling system. My goals are:
1) reliability
2) very low maintenance

The reliability part will be handled by the twin pumps in series. Should boost head as well

I define "low maintenance" as not having to take apart the system nor replace the coolant for 5 years. That's the goal at least, of course I won't be keeping the system that long, but the next owner might.

The only routine maintenance would be once-a-month vacuuming of air filters... that sort of thing...

The first question would be, what type of tubing should I use? It should have very low water permeability to minimize coolant loss. I'm thinking some stiff thick-wall plastic tubing, heat-formed to my desired shape so the relative lack of flexibility shouldn't be an issue...

Tygon silver antimicrobial tubes 1/2" ID

Silver = antimicrobial agent = no cleaning of scum required = no clogs in water blocks
Opaque nature = no light for algae to grow (cuts off photosynthesis)
Coolant loss is minimized because the tube has 3/4" OD = thick walls and added silver layer = less permeable = never need top ups
No need for additives = better cooling (additives retard the effectivness of water as a coolant)
Flexable enough for my needs.

Only cots 30 cents more than regular Tygon R3603!

also put in a resiovoir and paint it black or something so light cant get in so you have some extra coolant in there to increase the time between teardowns

Make sure you have all copper blocks too, if you're running straight water than you have to beware of corrosion.

Hard copper tubing to me would be the only viable solution to guarantee that kind of longevity. The Sony mediacenter systems that are watercooled use copper tubing. And even with Tygon Silver, I wonder about the plasticizer issues that every other type of vinyl tubing experiences causing issues over that length of span.

Unless you aren't performance minded, why would you plan on putting together a loop without any upgrades for 5 years? And if you aren't performance minded, why mess with watercooling at all? It just seems to me that air makes a lot more sense if you don't plan on any upgrades as overclocking doesn't make a lot of sense to me on a system that you don't plan on upgrading.

Also, with that kind of lifespan, you have to start thinking about some kind of o-ring conditioner for any o-rings in the loop. I personally put plain white petroleum jelly on mine when I install them.

Or you can just add some pond/aquarium algaecide and some iodine to prevent bacteria from building up .