I have good water pressure at the inlet from the city supply at 80lb. When I turn on one tap the pressure dropped to 40-60lb. Each additional tap drops another 20lb+. The flow almost slow to a trickle especially the shower when I flush the toilet. I believe my problem is low flow from the city. Replace the supply line will cost $$$$.

Is it possible to use a pressurized 20 gal tank to hold some water for sudden demand? Do I need a one way valve to prevent back pressure to the city supply.

Help..

What size is the pipe coming into your house? (1/2 inch, 3/4 inch, 1 inch... )

Do you have copper plumbing ?

Thanks for the quick reply.

It is 3/4 in copper pipe coming into the house. 60% of the inhouse pipes are 3/4in. I think the pipe coming from the city supply has mineral deposits. The pressure is good but flow is slow. I don't know of a way to back flush it. That's why I am thinking of a pressure tank.

Hi Alex,

"I have good water pressure at the inlet from the city supply at 80lb. When I turn on one tap the pressure dropped to 40-60 lb. Each additional tap drops another 20lb+."

With those words you just told me the cause of your problem and it isn't low flow from the city. The city provides the pressure ,(80 PSI, 45 PSI in the norm.) backed up by the volume oin the city main. While your house is piped according to code, 3/4" mains with 1/2" branches, your pipes are so constricted with mineral build up on the pipe walls that they will no longer carry the volume necessary to hold the pressure past the first draw. As the volume's cut down by each seceding draw so's the pressure.
I try to explain what's happening, rather then start with a repair option, so the asker will understand the scope and nature of the problem at hand.

How do we address this problem? Well for openers find out if the constriction's prevalent throughout the housepiping or just in one area. First thinhg is to call the utilities company and inform them of your pressure loss and ask them to check the meter for any restrictions. Next, to check the water service line from the street make surenothing's running in the house and open up the hose bib nearest to the line as it comes into the house. Turn it on full force. Now open up a cold water faucet in the house. There should be a small drop in pressure in the hose bib. Now start to open two or three cold water faucets. If the pressure falls to a trickle then the service line's clogged and should be replaced. If the hose bib still has good pressure then the problem's located in the house piping.

You ask,"Is it possible to use a pressurized 20 gal tank to hold some water for sudden demand? Do I need a one way valve to prevent back pressure to the city supply?"

At 80 PSI the city pressure far exceeds the normal city pressure of 45 PSI. (45 PSI is why water towers are 100 feet high) so your idea of installing a pressure tank won't do you any good. You don't have a pressue problem, you have a volume problem and all the pressure in the world won't do you any good unless it's backed up with the necessary volume. If it's determined that the problem's in the house piping the next step will be to determine ifall the pipes need to be replaces of if it's one area that's choking down your flow and that must be done on site. Hope I've explained things clearly enough.
Good luck, Tom