how many elbows is too much?

homeboundOctober 31, 2011

Is there any rule of thumb on whether 6 elbows on 1/2 copper is too many for good water flow to a shower mixer? I'm installing a Kohler with their large shower head. I can either use the existing supply lines with 5/6 elbows total front the crawlspace ceiling line below, or I can cut out 2/ea by routing more directly in the crawlspace. Do you think we will have a noticeable improvement in water flow or not? Thanks much.

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A copper 90deg elbow has a fitting insertion loss equal to 1" of straight copper pipe, therefore if you have 6 elbows it would have the same effect as adding another 6" on a straight run of pipe.

At the flow rates of a shower head the friction head loss would be almost negligible.

    Bookmark   October 31, 2011 at 11:59AM
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Thanks lazypup.

    Bookmark   November 1, 2011 at 12:03AM
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Just out of curiosity I worked it out.

Each elbow is has an insertion loss equivalent to 1" of 1/2" copper pipe so 6 elbows would be equivalent to adding 6" or 1/2foot of pipe.

At 3gpm the "Friction Head Loss" is 3.2psi/100ft of pipe which then equals 0.032psi/ft.

1/2ft of pipe would then cause a friction head loss of 0.16psi.

By contrast, if you were to raise the shower head 6" that would cause a "Vertical static head loss" of 0.2195psi so the 6 elbows would only cause approximately 1/13 as much loss as raising the shower head 6".

    Bookmark   November 1, 2011 at 3:35PM
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Very interesting. I WAS going to raise the shower head a few inches. Practically-speaking, do I need to rethink that? This is a first floor bathroom, if that helps.

    Bookmark   November 2, 2011 at 7:20AM
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The Vertical Static Head Loss is 0.434psi per foot of vertical rise and here again, the loss is so slight that it doesn't bear consideration.

    Bookmark   November 2, 2011 at 9:26AM
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For 1/2" pipe, the equivalent length is about one foot per 90, which will give you under 0.4psi loss at 3gpm for your 6 elbows.

Here is a link that might be useful: tubing handbook

    Bookmark   November 2, 2011 at 3:38PM
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