What size tube does the WSP50ARJ flush valve use?

The flush valve uses 3/8” OD tubing.

Will I lose any water pressure after installing thw WSP50ARJ filter?

You shouldn't notice any drop in pressure after installing this filter.

Is a Spin Down sediment filter necessary?

Spin down filters are generally recommended for use with well water or if you have high amounts of sediment. City water or Municipal water sources usually do not have high levels of residue but can have sediment issues; it depends on the quality of the source water and sediment that needs to be removed from the source water.

Can the Spin down sediment filters be cleaned and reused?

Yes. iSpring Spin Down Sediment Filters can be flushed, cleaned, and reused.

How frequently do I have to change the filter?

FCF600: 12 months; MRO600: 24 months; but it will depend on your daily usage and feed water quality.

Does this system reduce Fluoride & Arsenic? Does it reduce TDS?

Yes, this Reverse Osmosis system can reduce TDS, Arsenic and Fluoride.