Often the problem will appear to be a pressure issue when it is a volume or flow issue. A restirction in a line or just having a long line or under sized line could be the problem. If you install a pressure gauge you can check pressure. It should be above about 35 PSI. 35 PSI would be on the low side , but should be ok. Look at the gauge with all water off, then look at it when the water is on full in the bathtub. If the pressure is ok until you turn on the water than it is a flow problem. An easy way to install a pressure gauge is to just installan an ice making line kit with a gauge on the end of the line. This could be put any where convenient such as under a sink. One way to over come this is to install a pressure tank and check valve. The tank will give you the flow and the check valve will keep the flow going only into the tank or house. The in coming flow will be feeding your tank and house as the water is used, so the tank should last for a long time before you see a loss of pressure. I have had good results with this set up. One last thing to check is for clogged aerators at the sinks and shower heads. Waterman *If you have a Pressure Reducing Valve(PRV) on the main feed INSIDE the house, which should be just after the stop, loosen the nut, tighten the screw in clockwise to desired pressure and tighten the nut back up. Sometimes the screen in the PRV also gets plugged with sediment and needs to be cleaned. An easy way to determine your water pressure in the house is to purchase a gauge that screws onto the end of your hose bibb. You just screw it on and turn the hose bibb on and it will tell you the pressure in PSI at that point.* Cheers, QuiteSomething