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how many elbows is too much?

Posted by homebound (My Page) on
Mon, Oct 31, 11 at 8:32

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.

Follow-Up Postings:

RE: how many elbows is too much?

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.

RE: how many elbows is too much?

Thanks lazypup.

RE: how many elbows is too much?

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".

RE: how many elbows is too much?

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.

RE: how many elbows is too much?

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.

RE: how many elbows is too much?

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

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