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jce 04-11-2010 08:05 PM

correct size pipe for water lines
First , let me say we have low pressure , not sure what exactly can't find my pressure gauge.
There is a small kink in the main line coming into the house near the meter , so I'm thinking that is part of the problem.
The other problem is probably the cold water from NEAR the main supply is old galv. pipe being filled with buildup & shrank the inside diameter.
I need to replace the galvanized water pipe with copper .
The hot water line is already replaced with 1/2" copper , is 1/2" ok ?
From the main into the water heater and after the water heater is all 1/2" copper.
The service enter near the front of the house & all the water needs are in the rear , say 25' or so...
I was thinking of replacing everything with 3/4" just in the basement & then using all the existing 1/2" copper lines that run to 1st & 2nd floors.
Would/should that help , or would the larger line decrease the pressure?


Daniel Holzman 04-11-2010 08:12 PM

The pressure is fixed by the pressure at the meter. If you are on city water, pressure is typically around 50 psi, you can check with the utility to see what it is at your specific location. If you are on a well, pressure is regulated by a pressure switch, typically a well runs between 40 and 60 psi.

The pressure at your fixtures is a function of the starting pressure at the meter, and the pressure loss along the pipes leading to your fixture. The larger the pipe, the less pressure loss there is. For most houses, the basement is done in 3/4 inch copper, PVC or PEX, and the individual upstairs rooms are done in 1/2 inch copper, PVC or PEX. Installing larger diameter pipe reduces pressure loss, it does NOT compensate for inadequate pressure at the meter.

You indicate you have a kink in the line leading to the meter, this could certainly cause pressure loss before the meter, and should be fixed. If the municipality owns the line ahead of the meter, they should fix it, else it is your problem.

As to your question of whether 1/2 inch copper is adequate, that depends on the flow demand of your house. With high flow demand, i.e. two showers running simultaneously, or maybe a dishwasher and a washer running, 1/2 inch could lead to low pressure. You can't really go wrong with 3/4 inch pipe, unless you have unusual demands like a multiheaded shower or something odd like that.

jce 04-11-2010 08:23 PM

We have town water & in our old house in same township I had to install a pressure control/reduceer valve as the pressure was to high for the water heater, kept popping the blow off valve on heater & leaking. Pressure was high there , but we're about 3-4 miles from old house. I was surprised to see that the main coming into house was 1/2" copper. Guess maybe years ago that was considered good enough !
No unusual demands for water, single shower , no dishwasher....

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