We are building a new house. 2600sq feet with 2 stories, 2.5 baths, laundry, kitchen, and 2 exterior spigots. What cost savings should be expected? The builder's $600 credit to go to PEX seems a few multiples low.
I don't think so. Depends on the layout of the house though.
In smaller houses where all plumbing is within 20-30 feet or so and a manifold system can be utilized, it's a lot quicker and cheaper material-wise.
When you get into bigger more spread out houses where you have to revert to typical tree/branch distribution systems, you have to cut more fittings, which = more labor, and the pex fittings cost more than a copper fitting does.
Also keep in mind that pex is not a rigid material. It requires support at more frequent intervals as well as additional blocking in the walls to keep it from moving around.
You save time and money in one area, spend a little more somewhere else... the cost difference is usually minimal. The benefit? Pex is a reliable durable plastic product that performs well in wellwater systems where copper would fail due to high acidity.
Pex material cost is more expensive than copper, pex labor cost is cheaper than copper. Its usually around the same price at hte end of the day depending on the configuration, lengths and sizes of runs, so a $600 credit is not unreasonable.