The newer model Fluidmaster has a plastic screw type adjustment, not the metal bar w/ spring clip. The float is adjusted perfectly: the water fills right to the line embossed on the tank. Maybe I can explain the problem differently. After flushing, the bowl fills up fairly quickly. While the tank is filling up, water is shooting out fairly fast from the refill tube, into the overflow pipe. The water in the bowl is rippling while this is happening. Eventually, when the water reaches the marked line in the tank, the float arm raises and the fill valve shuts off, and the water stops rippling in the bowl. My concern is about the rippling water while the tank is filling. Is this water being wasted? Its actually my mother's toilet and she swears up and down that the rippling water indicates wasted water. I hope this description is better.

Agree with brickeyee....it's not air. Clogged line; blocked/stuck valve....something like that. If you're comfortable trouble-shooting lines and valves, go ahead and start looking. If not, this is plumber-time. Regardless, I suspect simple diagnosis and fix.

No... Each T&P valve requires a 3/4" line and if you are required drain pans, they also must have separate lines.

I appreciate your response Christopher. This is the first time we buy a manufactured home. We don’t need anything fancy, just reasonably durable and easy to maintain. I’ve been reading MH forums; some suggest a well-built home need : 2x6 exterior walls, 2x8 or 2x10 floor joist, 2x4 internal wall, OSB wrapped, 2x construction, low energy thermopane window. We’ve briefly talked to a salesperson, he emailed us a quote/confirmation sheet listing some standard and upgrade options without any structure information. To get those info what document should I ask for? Maybe Owner’s Manual & Warranty?