im losing coolant but there is no white smoke from my exhaust no coolant in my oil "i only put clean water now becuz im wasting too much money on coolant" and im 100% sure there is no leaks. Could this be because the water pump? I also have a d15 non vtec ecu while my engine is a d16 vtec could this be the problem?

 

If there is no external leak in engine compartment or in cabin, it (water) must be going out through tail pipe despite of no evidence such as white smoke. If ambient temp is high, it is hard to see steam out of tail pipe.

This is my best guess.

 

Running plain water will corrode and ruin your engine block and water pump. Use at least 30% antifreeze-coolant even if freezing isn't a concern.

It has to be going somewhere. Get under the car and look up for leaks around the back of the engine. There is a lot of plumbing there. If the water pump is leaking it will usually come out the side of the block near the alternator, or it might run all the way down to the crank pulley area. Plain water will be hard to see because it dries up right away. You could try isolating the heater core and the small parts on the intake manifold by running bypass hoses.