IamOiman wrote: I can also use bottle water if needed but have not felt the chlorine levels to be severe (the highest I have seen was 2.4 ppm for one month while I was not attending college in the summer according to my city's water report).

Chlorine and chloride are two different things.

Chlorine (and chloramine) are added in tiny amounts by water utilities as a disinfectant. You don't want even the small amounts of it in your brew water, but it's easily removed by an activated carbon filter. Chlorine (Cl₂) can even be treated simply by letting the water stand overnight.

Chloride is the Cl⁻ ion associated with salts like NaCl, KCl, CaCl₂, etc. It is not removed at all by activated carbon nor by conventional softeners, so if it's high (as in above 15 mg/L or above 50 mg/L depending on who you ask) you need to resort to something like RO to remove it. The chloride level in Cambridge is way up there - The 2016 report has it at 200 ppm (200 mg/L).

IamOiman wrote:The chloride levels range from 29-45ppm, but am unsure how exactly to approach this. Would this be tolerable for espresso machines or do I still need to use filters for them beyond what I retrieve from the Elkay bottle filters?

It sure beats the Cambridge water, but I think Synesso and probably La Marzocco would still call it unacceptable. If you had high alkalinity, that level of chloride might be tolerable, but your water report indicates only around 10 mg/L, which is very low. Your hardness (7 - 35 mg/L) is also low. I think you could get by with using your Elkay filtered water to fill your flojet bottle and then spiking it with about 80 - 100 mg/L potassium bicarbonate to bring the alkalinity up. But if it were me and I had a cherished Bosco Sorrento, I'd not use that water at all so as to avoid any worry about that chloride and possible corrosion. I'd fill my bottle with distilled or RO and spike that with the 80 - 100 mg/L potassium bicarb. (That's about 1.5 - 2.0 grams of potassium bicarb per 5 gallon jug.)

Note: With a flojet/bottle you could easily experiment with other water formulations. I don't want to divert this topic further into a water discussion, but I'll just say here that you can find a lot of info on that in the Water forum, and especially this thread: Good references on water treatment for coffee/espresso.

For $25 you can't go too far wrong. Depending on what you know about how long this was in service filter replacement may be in order but it is still a bargain. Not sure about the remineralization cartridge and espresso water but it should get you close with maybe some minor adjustment needed to be ideal.