What causes the water pressure to drop in the rest of the house when i turn on a fauwcet??

Question

when the water is turned on, at any place in my new house, the pressure flow drops real low every where else. (example) When the commode is flushed the pressure drops in the shower and/or dishwasher.

Answer 1

a lot of good answers here.  

another option may be the pipes are old and clogged which restrict the flow and "capacity" of the pipes.  therefore you cannot get sufficient water too all your fixtures.

time to repipe the house by a "licensed" plumber

Answer 2

Try the easiest solution first: make sure the main water shut off valve is all the way open.

Answer 3

Do you have whole house filters installed?  If they are 1-3 months old they can become so plugged with particulates that they slow the pressure throughout the whole house, and then become very noticeable when you are doing tasks that require large quantities of water.

How old is your house?  You may have some other plumbing issues.  Do you have well water or city water?  If it's a well and you haven't had much rain, your pump may have taken in some dirt or debris from the low water conditions.  If it's city water it may have some kind of plug from the main line to the line in your house causing the problem.  If it's a new house maybe the cut corners and used too small piping.  How long has it been doing this?  If it is recent, check that something didn't change recently to cause it.  Did you have any work done lately somewhere in your house? Maybe an incoming line was fractured.  IF all else fails, find a plumber.  Good luck.

Answer 4

This is very common. Flow problems are usually related to improper pipe sizing. For some crazy reason, many people skimp and cut corners when doing plumbing work. Good Luck!

Answer 5

probably too small a pipe was used in diameter from the meter into the cold water main, so by having too many faucets open makes it difficult to supply water to all at the same time at full pressure and full volume.(the leaky hose effect)