Water softener expenses

[Lance Schmidt]

Tenant said there’s water collecting in water softener (I installed for around $400 when I lived there previously. Single family). The property manager sent an independent water softener company over and they said it costs $2800 to replace. I can do it for $500 from Lowe’s.

Wanting help with avenues of resolving this. Should the tenant be responsible if they broke it? Can I just remove it or do I need to replace it?  It was in the listing when we rented it but can’t recall what the contract with the tenant said. 

Thanks!