Simply, when does insurance *usually* cover the cost of damage?

[Debbi Price]

I have no background in dealing with insurance companies and I feel like when I've spoken to agents I'm either getting conflicting information or I'm not explaining myself well enough.

While I understand the policies are different:

If I have a rental property that has a sewer line break/leak/backup, etc. My understanding is that insurance won't cover it. But, what I'm trying to understand is will insurance cover damaged caused by that leak, backup, etc. Like, if the sewer line issue will cost $5000 to fix but the issue caused $1500 in damage to a bathroom vanity, built-in cabinet, drywall, what have you and I have a $500 deductible,  even though the sewer line itself it not covered - would I be able to make a claim for the $1000 in damage?

I'm afraid of going into a property and either:

A) suddenly having a large damage bill that insurance won't help me out at all on

B) wasting money ($X,XXX-$XX,XXX) renovating by replacing water, sewer, mechanical, etc. to minimize the chance of something breaking.

I'm not talking about a system that has a known major issue but something that's 10 years old and will likely need to be replaced in 2-5 years. I'd rather save the cash and replace when needed but also don't want to risk an unexpected failure that insurance won't cover.