I don't have access to the lower drain. There's a deck around it. I have to use a sump pump to drain it unfortunately. It's a Hot Springs Flair.
You NEED to open those drains - when water molds gets into a tub, it will build up on uncirculated areas of the plumbing, and just keep coming back. Even using a "flush" chemical will not get into those area where water does not circulate. On the HotSpring tubs, those two areas are the drains, and any fountain which you do not use - in other words, if you don't flush out the water from any system, it can harbor the water mold.
I don't know what you need to do to open those drains, but you certainly need to have access to the motor compartment door, so I would guess that you should be able to get to the drains somehow. If it is just unbelievable work, do it anyway, or you will not be rid of the water mold. Once you DO gain access to the drains, you can always screw a short garden hose onto them, and lay it in a more accessible spot - with a simple cap on the end. That way if this ever comes up again you can superchlorinate, and then open the caps for a couple of minutes to clear the drain plumbing (and draw chlorine into those systems).
One of your drains should have a valve like this on it:
Both of the drains should have a cap like this:
Buy a second valve, and extend the drains with a short garden hose - and that way you can 'flush' those plumbing sections with ease anytime you want to. Not only that, but if you have sufficient drainage, you could actually USE the built-in drain instead of pumping.
Some models of Limelight tubs have the drains on a section of flexible PVC INSIDE the motor compartment. If you are that lucky, you only have to open the door, reach in and let some water out to flush the plumbing in that area. This is an image I found online, NOT a Limelight, but it shows how some of the earlier units had the main drain coming out of the motor compartment. You may even be able to change over to this type of system if your deck precludes any access to the built-in drain caps down at the bottom/outside of the tub.
HTH
