I have a 1/2" pipe system in my house. The water pressure is very good if there is only 1 source of water open (bathroom faucet, kitchen faucet); but if there are 2 sources of water open then it is very low pressure/flow. Or if I flush the toilet and the other sink will have low flow.

Is there any way I can improve this? Thank you.

marked as duplicate by Ecnerwal, mmathis, ThreePhaseEel, Chris Cudmore, Machavity Oct 12 '17 at 15:23

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  • What's the pressure coming in from the utility like, or do you have a well instead? – ThreePhaseEel May 28 '17 at 2:37
  • This could be due to a constriction in the system at a single point. A possibility is the cut off valve for your entire house or the cut-off valve at your water meter if you are on a public supply. Check these valves to see that they are fully open. In our tract house built 1970 there is a valve on the city side of the meter which is what I use to turn off the water to the house when I need to. We have a set of brass gate valves in the ground which are corroded and I believe inoperable. I once tried to use one and had difficulty getting it back into service. – Jim Stewart May 28 '17 at 9:26
  • @isherwood, I have not checked the water supply from the city but it is high enough to do my car wash without using pressure pump. It makes noise in the pipes(water hammer) when the water is open. I have checked all the valves and they are fully open, thanks. The house was built in 1960. – TomN May 29 '17 at 14:15
  • Use the add a comment link underneath each post to address the author of that post. – Niall C. May 29 '17 at 14:25

There are 2 possibilities to correct this problem unless, as described in previous answers, there is a restriction somewhere in the piping, bad valve, plugged line, etc. If the problem is not one of these then you need to raise the incoming pressure, if possible or increase the size of the incoming pipe.

To increase the size of the piping, first check to see what is the size of the incoming piping from the street. If it is a size larger than the 1/2" you have in the house, then I would change the size of the piping to 3/4" from the larger street size all the way to the water heater. By doing this you are supplying both the hot and cold water supplies with it's own 1/2" supply line. Any take off feed between the incoming water and the water heater would be by a 3/4"X3/4"X1/2" reducing tee.

I do not know what the codes are in your area so you may be able to do it yourself or you may need to have a registered plumber do the work.

I would not use "shark bite" type fittings since they have some restriction built into them. If you have a 1/2" water meter, it will not add much restriction due to its short length.

To raise the pressure you could adjust the PRV in the supply line if you have one. If you don't have one then you are limited to the pressure in the supply line.

  • all I can see from the coming line is 0.5" pipe fed to my house, the rest from the city to our house is buried, I can't confirm it. Probably, I have to live with it right now since the basement is finished, thanks. – TomN May 29 '17 at 14:23

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