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#1
11-06-2009, 08:31 PM
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Low pressure from PEX manifold
I just installed a PEX manifold system and have significantly lower pressure than I did with my galvanized system. The copper pipe from the street is 3/4, which I transitioned to 3/4 PEX. I ran straight to the water heater and have less than three feet of pipe from the water heater to a five port manifold and also about three feet of water from the T to the water heater to a ten port cold water manifold. There were no leaks that I could find, so i don't think I'm losing pressure there.
What could cause a loss in pressure like this? Thanks 
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#2
11-06-2009, 08:35 PM
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3/4" PEX is smaller then copper sizing.
How many bathrooms do you have?
__________________
Consumer report on the new toilets How Green Are Low-Flow Toilets? Terry Love Plumbing Shopping Cart
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#3
11-06-2009, 08:56 PM
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Two full baths.
In the previous system, the copper transitioned to galzanized as it passed the water heater. How is the diameter of 3/4 galvanized compared to 3/4 PEX? The faucets that are closer to the manifold have much better pressure than the ones furthest away if that helps ID the problem.
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#4
11-06-2009, 09:31 PM
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__________________
Consumer report on the new toilets How Green Are Low-Flow Toilets? Terry Love Plumbing Shopping Cart
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#5
11-06-2009, 09:34 PM
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What size is the manifold and the pipes leaving it?
Galvanized could be quite small ID after a long time. It's hard to compare old stuff with new pipe. Could be clean, could be the opening of a soda straw or smaller.
__________________
Jim DeBruycker Important note - I'm not a pro FWIW - Don't try to buy a phone from Nokia on-line
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#6
11-07-2009, 06:23 AM
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I thought I should have one inch from the meter as well, but it is definitely 3/4. I have enough copper to run it to the water heater and just up to the manifolds. I'll try that and see if it helps.
Thanks
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#7
11-07-2009, 09:05 AM
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pipe
3/4" PEX has only slightly higher capacity than 1/2" copper. What size are the lines from the manifold to the faucets. If they are small, or overly long, that will be the most likely source of your poor pressure.
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#8
11-08-2009, 06:43 AM
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From the manifolds to the faucets it is 1/2 PEX. The shorter lines were OK, but the longer ones were terrible.
I replaced the 3/4 PEX with 3/4 Copper and that has helped. The shorter lines now have adequate pressure. I ran 3/4 PEX on my longest run, to the kitchen, but the pressure is sill low. It's about a 30 foot span. I guess I'll have to go 3/4 copper there too..... I've learned a lot with this if nothing else. I plan on building a house in the next few yeas and this is valuable information. Thanks to all those who replied.
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