Neither one will make any difference in water pressure.
Your water pressure is low. Consequently, when cold water is diverted to another application such as a toilet or a sink, the amount of cold water available at the shower mixing valve decreases as the low pressure is unable to keep up with the shower's demand. This causes a hotter mixture at the shower head. The solution is to either improve the cold water supply to the shower or to replace the shower control valve with a temperature compensating type. Pressure balancing is the cheapest and simply changes the shower temperature according to the pressure in the cold and hot water lines. When the toilet or sink is used, reduced pressure to the shower valve is detected and the valve reduces the hot water pressure, thereby maintaining the temperature. The more sophisticated approach is a thermostatic shower control valve. These are significantly more expensive, but will not reduce the pressure at the shower head (a drawback of the pressure balancing valve). The thermostatic valve would be required when one shower control valve is operating several shower heads. Moen, Kohler and Delta all make both types of control valves. They can be readily obtained from a local plumbing supply house.
The flow of water from the shower creates a low-pressure area inside the shower stall, causing the shower curtain to be drawn inward due to the difference in pressure between the inside and outside of the shower. This phenomenon is called the Bernoulli principle, where higher speed of a fluid (in this case, the water spray) results in lower pressure.
This does vary slightly according to the shower, but for a shower without a pump, using a gravity feed, a water pressure of at least 0.1 bar is recommended. If your water pressure is low you will need to install a pumped shower.
More than likely a blockage, leak, or bad installation. If some other showers, toilets, and sinks are having problems with running water then it's likely a problem with the entire water system, usually bad parts or a leak.
Because it effects the water pressure of the shower. This causes the temperature of the water in the shower to also change.
There is a screen and/or a water saver in the shower head. The screen may be plugged with sediment from in the water.
Its a loss in water pressure to the shower.
May be build up in the valve itself or the shower head.
I will say you can take a look at aquasana shower water filter.
The simplest and lowest cost solution is to replace the shower head with one designed to increase the pressure.
Yes and what is the question?
when the water pressure is low in the shower