Based off your comment, here is my suggestion...
You can use QGIS to create a map of the drains. There will still be some things you will need to work out, but this program will work very well for creating a simple map for you to reference.
I would suggest finding some aerial imagery to use as a guide. You can check your local government and work your way up the hierarchy until you find someone that has relatively recent (leaf-off in case there are a lot of trees) imagery. You could then load that up into QGIS as a reference.
If you're getting GPS locations from your phone, you can write down the lat/long information and trying to find those particular locations in QGIS. They will not be as accurate so it will be nice to have an aerial image to help you find the correct locations.
You should be able to create a simple map using the two items. However, the map will not be as accurate as you can make it. It would work as a general reference so you have a very, very general idea of where something would be located. You may be able to create the maps, but the person using them might need to wander around a bit before finding the actual drains later on due to inaccurate GPS coordinates.
There will be other issues you will need to consider as well. With imagery, you will need to consider possible alignment/measurement issues depending on if the image is in a coordinate system or just a plain image. You would also need to worry about the inaccuracy of whatever GPS unit you're using to collect. Plus, you would need to worry about how to properly use the software and tools to get the best result.