Instruction manual is very vague in how to change the needle. You will need to use the big needle with big tip if using water based acrylic paints as they are thick and I was doing an entire house so wanted a large spray pattern. I had to take the gun apart to figure out how to remove the needle. I was worried that the needle was rotated in position to lock and I may break it if I tried to pull out. Turns out you just pull the needle straight out (no turning required) and a plastic clamp holds it in place. The tool can be used to remove the needle but it just rotates so it gets behind the plastic on the needle then pull straight out. Pliers can also be used just do not damage the needle tip. Putting back in requires it to be aligned properly as the needle does have a flat portion where it clamps. Do not use gun on water based primers or or sealers with ability to seal cracks as this is hard to clean and gums up or plugs the gun. Make sure the paint will work with sprayers as some water based paints for sealing cracks in concrete can only be rolled on. I used this gun to do an entire house with wall (both concrete) with water based high end Nippon paints. I used weatherbond in sheen. I ended up adding water to the paint about 5% which made it flow properly for an even pattern. I did this by adding water to the entire paint container then mix then keep refilling. If the acrylic paint is too thick it will not flow good, may have start stops, and may drip from nozzle. With proper dilution these issues go away. I also ended up drilling a hole in the paint pickup tube inside the spray gun container and drilled a hole in the plastic pickup tube and screwed it in place. The reason is I found the pickup tube continually kept falling out of place and the sprayer stopped working and I had to open the paint container to put it back in place which was a mess. After the 3rd time I screwed it in place with a tiny screw and problem solved. This gun is a lot of work to clean but it did end up handling water based acrylic paints that were fairly thick very well which I was worried about as not sure if enough air velocity to move thicker paint. With a little bit of water to thin the paint it worked great. Make sure you do not go over manufacturers dilution which is often
