Internal parts are metal and not plastic, etc. 

A lead certified painter has to remove all loose paint, basically lay out plastic everywhere to make sure nothing gets in the ground then scrape the loose paint until you have a solid base and then paint over it.

Go deep, my companion.

The other thing you can do is put some plastic (like they use to hold in insulation) under the home and tack it to the floor joists. 

It's also an old house I purchased a year ago and I don't have records as to when that drain stopper switch was replaced.One thing, with old tenants, I had to cover fee to unclog drain when it was clearly one of the tenants who dropped a big piece of plastic in the drain hole.

Since then, the tenant has been placing a plastic sheet on the inside of the window and taping it up to seal air leaks from the outside.

I do not want to use the plastic boxes with keys as they are easy to break into.

Is this a ceramic or plastic tub ? 

This is more of a hard plastic mesh and might not lay down as easily as the truck is driving forward.

She is not getting him plastic surgery, its blood transfusions!