I currently have a Samsung Smarthings hub on main floor. I also bought one Samsung water detector & originally planned to put it in my basement near a water heater. However, it didn’t seem to register or work at all when I put the water sensor down there. I moved it upstairs to a bathroom (about 20ft from Samsung Hub) and it now works great.
I plan to get some more of these Samsung water sensors for throughout the house, but I guess in order to have them work properly in the basement, I need some sort of range extender down there as well, correct?
Other than getting another Samsung hub, any recommendations on a range extender/hub that works with the Samsung water sensor AND some Sengled Smart bulbs I want to put down there as well (that need an extender too)?
I see a Wink hub and was hoping this would work with my samsung water sensor and Sengled bulbs down in the basement
Both that sensor and the Sengled bulbs are zigbee devices. Zigbee home automation (ZHA 1.2), which is the protocol that smartthings uses to communicate with those devices, is a mesh network. So you don’t need a range extender: you need a zigbee device that can act as a repeater. Fortunately, almost all plug-in or mains powered zigbee devices which work with SmartThings Will automatically act as a repeater, so you will have a lot of choices.
We do need to know whether you are in the US or UK, as the device selection does vary somewhat.
Meanwhile, read the following FAQ. Start with post 11 in that thread, read it, and then go back up to the top and read the whole thread. It will answer most of your questions On improving communications efficiency. 
You will not be able to use the wink hub for this purpose, by the way. Zigbee home automation only allows for one primary coordinator per network, so you have to choose between the wink hub or the smartthings hub, you cannot use both with the same zigbee devices.
But again, it’s likely that all you need is a repeater device somewhere between the basement and your smartthings hub.
If you are in the US, the iris smart plug is very popular as it happens to contain two radios and can act as a repeater for both Z wave and Zigbee.
https://www.lowes.com/pd/Iris-120-Volt-White-Smart-Plug/999925330
But there are also a lot of zigbee-only plug-in modules that will work just fine.
So you can use the plug-in module (which we call a “pocket socket” in this forum to distinguish it from an in wall receptacle or an in wall micro) and get double use out of it: it will automatically act as a repeater, and then you also have it as a controlled on/off switch for a device plugged into it. 