States are coming down on private water systems, requireing alot more chlorine and samples sent to testing.  

The pool almost had to be closed down last year due to the mustard algae causing the chlorination levels to be high.  

Outside is a different story, as tree roots or shifts in the earth can crack a sewer line.If the smell is coming from the water lines, first thing to do is have the water tested for chlorine level.

You fix the leak, chop your walls open at the bottom to inspect, physical clear out the mold and spray surfaces with chlorine bleach and/or soaking agents (great stuff from homedepot.com) for absorbent surfaces. 

This multi has 6 large trash bins that my live-in maint guy is not happy about chlorinating & hosing out every week. 

Chlorine will rust a bicycle stored in the same room.

If they wanted it changed (I've passed on poly houses before- chlorine wears out the joints) the time to bring it up was when still under contract. 

Okay so in my apartments I tell the previous owner (I recently just bought them) that I plan on going in once a month and changing the air filter.This way the units can be inspected some and also I know the power bill won't be as high for the tenant and the low air flow won't burn out the fan motors faster.The seller mentioned to me that I should also check the toilets as well.The seller stated that tenants like to put those chlorox bleach tablets in the toilets and it eats up the flapper valves.This causes a water leak and runs up the water bill for the landlord.Here the water is included in the total rent payment each month.So should I ban the chlorine tablets from the toilets or should I just replace the flappers all at once??

A pool or spa test kit is like that, where you measure the amount of chlorine or bromine present.

I'm only one of a few hundred still alive who do what I do ("legacy" systems - OpenVMS).Also was a liturgical musician for 40+ years, amateur musician, did HVAC back in the chlorinated halo-carbon days, did pro-audio, ran a recording studio briefly (I was otherwise out of work most of 1985), have done community college telecourse broadcasting, TV production (camera, audio, editing), low-voltage wiring systems. 50+ years experience public speaking including business presentations, international technical symposia and liturgical settings.