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Thread: Water supply question, small cottage

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  1. #1
    DIY Junior Member Shelly296's Avatar
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    Default Water supply question, small cottage

    Bought a foreclosure house that was not winterized properly, so I have no idea how well the water lines originally worked. What I am doing is running new pex to most of the fixtures. This is a 900 square foot cottage. Will have washer, one full bath, kitchen sink, dishwasher and fridge water line. Installed a new water pump and pressure tank on the inch and a quarter well. I put a hose attachment on so I could get water while working on the house. I get about 6 gallons per minute.

    The original lines are 1/2 inch copper to the pump and then 3/8 inch copper to new cpvc 1/2 inch. My question is: I would like to attach 3/4 inch pex to the 3/8 inch copper as a main trunk line and then branch off with 1/2 inch pex. Can I do this? I cannot replace the 3/8 inch copper to anything larger. Or do I run everything in 1/2 inch pex?

    Thanks for any support.

    Shelly

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    Retired Defense Industry Engineer jadnashua's Avatar
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    having a section of 3/8" copper as your feed is going to impact the operation radically, regardless of what you use elsewhere after it. My opinion, do what it takes to make the supply line to the house something that would pass codes and be able to provide useful service; 3/8" in the line isn't.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Junior Member Shelly296's Avatar
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    It is really going to take some doing to get 3/4 inch pex coming from the well pump. But, i was just a little bit hopeful another plan would work. Can you ever go from a smaller pipe to a larger one? Would you even notice the difference since the water is restricted from the start?

    Looks like i'll be getting into the slab tomorrow and running some bigger lines. The largest pex crimp tool i have is 3/4 inch. I have a friend with a one inch crimp tool that i could borrow. Would the 3/4 inch pex be a large enough trunk line?

    Shelly

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Local codes typically dictate how large the supply pipe needs to be. Most of the time on the supply line from the pump to the house, they tend to use something like 1 to 1.5", and usually not pex. The longer the run, the smaller the pipe, the more friction you have and to get decent flow, you need to go up in size. Once in the house, bigger lines to a group, such as the bathroom is usually done, then branch to smaller pipe to the individual fixtures. 1/2" pex is fine for one fixture (assuming it is fed properly), but is not sufficient for multiple fixtures. 3/4" pex isn't much bigger than 1/2" copper on the ID, and that may be small for a main supply. One of the pros will probably have the code info at hand. How long is the run from the wellhead to the cottage?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member Shelly296's Avatar
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    It's inch and 1/4 line coming into well and 1/2 inch copper coming out and then reducing to 3/8 inch copper. The well head is just on the other side of the wall to where the pump sits. Well was driven by hand about 3 feet away from the house exterior wall and goes under the house 4 feet and then into the utility room. From there the longest pipe run will be about 30 feet. The utility room is on a slab. It used to be the back porch and then was enclosed. The rest of the cottage is on a crawlspace, and now i know why it's called a crawlspace! She's pretty tight!

    Shelly

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    DIY Junior Member Shelly296's Avatar
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    I noticed that the pex ID is about a size under what pex and cpvc is. That's why i was wondering if should run 1 inch pex. This is a small, summer cottage.

    I was just planning to run a main trunk line and branch off with 1/2 inch to each fixture.

    Shelly

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    Forum Admin, Expert Plumber Terry's Avatar
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    A one bath home shouid have at least a 3/4" water service.
    We only run two fixtures on a 1/2" line.
    The icemaker line is a freebie!

    1" PEX would be even better for a water service line.

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    Test, Don't Guess! cacher_chick's Avatar
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    1" pex or 3/4 copper for a cottage that size. The water heater should be supplied by the same.
    You could homerun 1/2" pex off a manifold to the individual fixtures if you wanted to go that route.

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    DIY Junior Member Shelly296's Avatar
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    Thank you all so much. Looks like I will be going with the one inch pex line because I will be pushing that line through a wall and sill plate running at an angle to get into the crawl space. Would really like to run a manifold system but I'm going to have enough trouble getting the hot and cold lines through! As you may have noticed, I'm not a pro, but I do like things to work correctly. I know just enough to get myself in trouble. Anyway, I think I spent about a day reading on how to correctly vent . I'm sure to be back with some more questions. I'm sure you are all excited to hear that....

    Shelly

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