Main water line-too small?

Liquid moving inside pipes causes friction among other things. Dynamic, or working, pressure (when water is flowing through the pipe) will be lower due to higher friction caused by smaller diameter pipe. If we draw 5gpm, at the end of a 50ft straight run of 1/2" K type copper pipe, pressure loss would be 10.05PSI vs 1.85PSI for 3/4 K type. In other words, more pressure is used to push 5gpm of water through 1/2" pipe than thru 3/4". Without increasing pressure, more volume can be delivered by larger size pipe. So you are correct.

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Thanks Simon! Hopefully my client won’t ask be to explain that, but it is going into my library just in case. :+1: :wink:

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Put a test gauge on a 1/2” main or a 3/4” main what will it read? It will read the same pressure.

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The pressure will read the same even if the main is 1/4" until the water starts moving. There is no energy (pressure) loss when the water isn’t flowing.

wow!! bet the owner loved that

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How many flushes does it take to run two toilets continuously for an hour straight?

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Right! Pressure and Volume are two different factors to consider. You may get a 55psi (Good Reading) pressure measurement at the entry point, but when several faucets are open at the same time, the caudal/volume that can go by the cross section of the 1/2" pipe may not be sufficient to run all the showers and the cloth washer simultaneously. However, not a deal-breaker. For a small household family it may work perfectly (<4 persons). More people will generate a lot of insatisfaction among the inhabitants. Upgrading a whole house from 1/2" to 3/4" or 1" piping may be not only expensive, but a complicated task having to open the walls and floors.

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What more is there to say?

What does your SOP say you have to discuss in the report?
No one wants to know what you think, they want to know what does not function as intended.

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