I am running all new water supply in an old house (c 1884). The incoming line from the meter is 1" galvanized (no idea how much mineral buildup is inside).

  1. Will it be sufficient to replace all of the plumbing using 3/4" manifolds (one hot & one cold) with 1/2" supplies to the fixtures? There is currently a mix of PVC, copper, and galvanized being used and water pressure at the fixtures is tolerable, but affected greatly by flushing toilets or running the washing machine. I would hope for better with a new system -is that likely?

  2. There are both a whole-house sediment filter and water softener. Any special considerations (order/pipe size) for these with a PEX system? Currently they are connected using 1/2" pipe connected to the 1" inlet (by another home owner), although the water filter will accept 1".


If you're going to re-build all the piping only for this pressure issue I suggest you to first try adding a flow reducers to toilets, washing machines and to all those supplies where a reduced flow is still acceptable. In this case pressure unbalancing will be reduced without affecting comfort or efficiency.

Anyway I suggest you to keep the cold piping as big as you can (1" is good) for the main conduit (where it splits to water heater and to each bathroom and kitchen lines where you can start with 3/4) as it will greately reduce pressure unbalances. If you use PEX, check pipe is PEX-c using lower grades (a or b) will be penny-savy pound-foolish. Pex c mean it's phisically-reticolated, pex-b is temperature-reticolated (but sometimes the last 'hot bath' is never done leading to premature failures) and pex-a is chemically-reticolated won't be guaranteed to last 50 years but it's not as bad as pex-b.

There are also 'unreticolated' pipes, those should be absolutely avoided as may break with hot water or high pressures so look for *PE-Xc/Al/PE-Xc * printed on pipe.

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  • I have no idea where you got the term 'reticolated' - it does not exist. Your description of the manufacture of PEX variants is quite incorrect. PEX-C is crosslinked using electron beams and generally considered the worst of the three main types. – SomeoneSomewhereSupportsMonica Apr 20 '19 at 7:52

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