Before the rehab of it the humidifier ran constantly but now it's rarely running.

I found humidity to be an issue in the garden so a humidifier as well!

In addition your utility bill will be higher and the system will not properly de-humidify.

I went to the house twice and the first time there was some kind of loud portable device running in there--maybe a de-humidifier?

The two rear units had de humidifiers running.

Hi,I had a flood in one of my basements (not too high less than an inch), now after I got out the water I want to put a dehumidifier,I see there are ones with a pump and ones without a pump, what's the difference? and...

Replacement is the issue.Additions Bedroom Bathroom Deck Garage Porch Patio Heating & Air Conditioning Heating system Central air conditioning Furnace Duct work Central humidifier Filtration system Lawn & Grounds Landscaping Driveway Walkway Fence Retaining wall Sprinkler system Swimming pool Miscellaneous Storm windows, doors New roof Central vacuum Wiring upgrades Satellite dish Security system Plumbing Septic system Water heater Soft water system Filtration system [b]Interior Improvements[/b] Built-in appliances Kitchen modernization Flooring Wall-to-wall carpeting Insulation Attic Walls Floors Pipes and duct workThis is not a finished list this is just an example.

Things I remove:Garbage disposal, ceiling fans, kitchen faucet sprayer, all electric in a detached garage, most of the electric in an unfinished basement, humidifiers, locks on interiors doors (teach the kids how to knock), door bells, shower doors, showerhead on a hose, flouresent shop lightsThings I add:Door stoppers, motion lights (in a rough area), deadbolts to exterior doorsThings I replace:Gate valves replaced with ball valvesOld houses that have a "barrel trap" on the tub get replaced with a P trapAny plumbing repairs are redone in PEX, even if the rest of the plumbing is copper or galvanized

A tip I wanted to give you is to have a humidifier.

The second cause is high indoor humidity, thats why if you have a whole house humidifier the recommended humidity setting is lower the lower your expected outdoor air temperature is, to prevent condensation.