Water Leak in basement please help

I found a water leak running down into the basement. There is some water damage behind the wall.. I cut a hole into the bottom of the wall it and have been trying to locate the cause by checking different things. Filled bathroom tub upstairs and when I opened the drain the water dripped down the leak. Thought I found the source. Turned off the water to the bathroom and have not used that tub/shower, sink or toilet. Things seems to be ok until I flushed the toilet in the first floor (directly under the upstairs bathroom) and washed dishes in the kitchen sink (first floor but opposite side of the house).. l'm not sure which of the two was the new water problem.. will wait till leak drys and dry running water in kitchen sink again.
What can this problem be? At first I thought it was the drain in my upstairs tub.. the tub would slowly drain even while drain was closed and twice while draining tub found water came through fan in ceiling in the first floor bathroom (directly under upstairs bathroom). We stopped using upstairs tub thinking for the time.. and didn't have a problem with the shower.. but know I'm stumped that the downstairs leak seems to be caused by more that one thing. Please help and advise. I will call a plumber but would like to narrow things down first. Thanks you for any help.
Also.. been getting little slow black moths near leak in basement. Septic is nearby but has been cleaned out a year ago...

A joint/pipe in the drainline where the fixtures share common piping?
(leaks after the point they are all joined together...?)

thanks. do you think I should try to figure out more about the leak or just go ahead and get a plumber. Would that be an expensive thing to have fixed?

Depends...how open is the piping? If he has to tear out walls or ceilings to find the problem, it could take a long time and time is money, not counting fixing them back to normal. The actual fix could be easy once it is discovered. If the pipes are cast iron, or galvanized, they could be rotted through, and a total rework might be called for. If it isn't a simple repair, you would have to bring the parts replaced up to code, which could be a big deal as well. You can generally remove and replace, but there is a dividing line where they make sure everything done is up to the current code. I don't know the exact point, and I'm sure it varies by locale.

urgent who should I call- plumber or septic?

This morning we opened up the wall in the basement to pinpoint water leak (picts attached).. who should I call to come in- a septic person or plumber? Water is coming through from the cement wall from the outside..can see on top left corner on pict- this is behind the wood beam.. it's the cement wall to outside of house.) I believe my water main line is right there as well as my septic. There a bugs on the wet cement and moth flies (on photo) in the basement. It doesn't smell bad. When I use the tub, sinks, etc from other areas of the house water leaks in this spot. Nothing moving on the water meter.
Any advise would be helpful.. ps- we had the septic take clean out one year ago.

Thank you.

can you enlarge the pics (or put them online and post a link?)

picts

are these better for viewing?

how deep is it outside? would it be possible for you to dig it up outside and see what's happening? as far as who to call, I'd call a plumber.

too deep to dig- got someone over today to empty the septic tank- turns out it was full.. empty now but water still coming through cement. Will call Monday am to have plumber come out. Is it possible that this can be coming from the town plumbing water supply to the house? Should I call them as well?

Yes, it could be the supply line. Depending on where you live, the water company may own it or it could be yours. Where is the meter? Is there a shutoff near the street? If it is leaking after the meter, (say it's at the street), you should be able to tell from the reading on the meter if water is running; otherwise, it's harder. I've heard that if the water company finds a leak, they may shut the water off and leave you without until it gets fixed...can't say that with certainty as I've never experienced it.

getting closer

My town's water dept sent someone over this morning. He shut the water supply off to the house and it did not make a difference. He thought it was rain/ground water but it has not rained in a while. After he left I looked at the leak again- ran a bath and could really see the water running down through the cement wall crack in basement from outside when I let the water out- and, the same thing happens when I flushed an upstairs toliet... must be a bad connect outside the house.. or leak in pipe outside under ground. I have someone coming over tomorrow morning to take a look and hopefully I have an answer.

Anyone ever have the same problem?

Thanks for everyones help and advice.. especially about warning me that the water might be shut off if the main was the problem. I made sure we all showered before the water dept person came over and put plenty of water in my fridge just in case.

Yep - I just had to fix something similar to that. Once that pipe rots through it will start to close up inside, which makes things flow slower. After that it backs up through that hole and it has to go somewhere. I could almost shove a screwdriver through the rotted CI on ours.

thanks you were right about leak but tub drain replacement question

Thank you MA. Journeyman and MG.. you were both right!! Someone came over today to look and will repair tomorrow.

Now that I'm having this repair done I have one last question before the repair person comes tomorrow-
Since I also had an earlier problem with the upstairs tub/shower (drain stopper not holding water - seeps out and when draining tub noticed water came into bathroom directly below out of ceiling vent).

Here's my question- I've been thinking about re-doing this bathroom (new tub, tiles, wallpaper...) Do I have them repair the drain tomorrow as well (I guess this means a hole in the wall to get to it?) or do just not use this tub for now. Does this part get replaced when a new tub get put in.. and will I be spending the same money twice.. or should I fix it now?
Thanks again..

I'd consider waiting until you do the remodel. It is almost certain that the hookup would need to be moved, at least a little, as it is very rare for a new tub to line up exactly with the old one. You may need to tear out a lot of old drains, and doing it while you are remodeling rather than piecemeal makes more sense, at least to me.

Discuss it with the plumber.