10 gallons per minute from 1/2" line?

Is it correct to think that if 4 body shower heads are fed from one 1/2" line the volume per head will be reduced to one forth of the 1/2 inch line with the same pressure. The shower heads (kohler k-8506) use 2.6 gallons per minute for a total of 10 gallons per minute. Will one 1/2" line hold enough water at 60 psi to get the maximum performance from the shower heads?
Thanks for any help
u4ick
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u4ick wrote:

Yes........except.....the shower control (faucet) very likely has internal restrictions built in which will greatly limit the total flow. If this is a new install you're considering, mock up the connections in the backyard (or somewhere) using the brand/model of shower control in question. Measure flow into a bucket.
Jim
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Thanks for the help. The conrol valves are 3/4" being fed by 1" lines of hot and cold. Great idea about laying it out and testing the flow -- the plumbing is already in the wall in rough out stage which may allow us to test it.
Speedy Jim wrote:

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Go to a site that offers lawn sprinkler design information. It will give GPM for various pipe sizes and supply pressures. Here's one, but it doesn't give pipe sizes as small as 1/2", but 5/8" allow 10 GPM, so 1/2" would be less:
http://www.irrigationtutorials.com/sprinkler03.htm
Ray
u4ick wrote:

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Forget all the math. If you have four showers going at the same time, chances are someone is not getting enough hot water. Practical applications sometimes outweigh all the facts you see on paper.
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He is describing four shower heads in one shower, not four individual showers.
Bill
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You hear about the married couple who got a split electric blanket? Their controls got switched one night. He's too hot, so he keeps turning it down. She's too cold, she keeps turning it up.
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A problem like this obviously can be solved several ways. I think that it can be done easiest graphically. You take each system ---the supply line with its respective fittings, the shower head and any other line restrictions---and plot their flow characteristics separately and then graphically put them all together to define the whole system. This will probably sound more complicated and/or confusing than it actually is: For example: 1.0 Measure and calculate the number of equivalent feet in your supply line. This includes the length of the pipe plus the number of feet added due to various fittings. The line will have a pressure drop/100 ft as a function of the flow going through it. The line/fitting resistances can be found via various available references (using Goggle is one source to find them) .So first step is to vary the flow and calculate a delta P for each flow. Plot Delta P (Y axis) vs Flow (X axis). 2.0 Characteristics of the shower head. Per Kohler--2.6 GPM at 60 psi (since there has to be a pressure drop associated with the flow and I will assume it's 60) Use whatever it is anyway. I also will assume that it's flow characteristic is GPM=f(sq. root of delta P). So what this means is that GPM=K*sq root Delta P. Solve for K which is = 2.6/sq rt 60. Now for a bunch of different Delta P's calculate GPM (using the K just calculated). For four shower heads, multiply the GPM just calculated by 4 for the same Delta P. As before, plot Delta P vs GPM (4 shower heads) on the same curve as the supply line. 3.0 Merge the two plots together to get a total system characteristic. You do this by looking at a GPM and then add the Delta P for the line and the Delta P for the shower head and plot that resulting Delta P for the same flow. This will result in a curve that represents the whole system. The input to the supply line defines the starting upstream pressure and the exit of the shower head is the downstream pressure (ambient) so for all practical purposes, the supply pressure is equivalent to the system Delta P. So now plug in any Delta P in the curve (60 in this case) and look down to see what the resulting flow will be. The beauty of the plot is that you can get a system flow for any supply pressure. Obviously, the accuracy of the resulting flow is dependent on just how well you've describe all the system resistances--such as the shower valve itself etc. Worst case is to get that info from the manufacture himself--their customer service or tech support are usually quite helpful. I've used this method of getting answers for some systems that otherwise would be much more difficult to obtain. MLD
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Use 3/4". You might save $10 using the 1/2" and regret it later. I did plumbing for years. I had a rule of thumb. !/2" pipe is only for a SINGLE device .

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You are a wise man.
Who needs four showers at once, anyhow? You running a gym or a spa?
Hint: Use full flow shutoffs. Ball valves or gate valves have a lot less pressure loss than globe or angle valves.
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Measure flow now, I have 1/2 @ apx 60 psi and get 5 gpm. . So maybe only 1.25 for 4 heads
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Thanks for all the information - the irrigation sites provided some very useful information. I will keep working on the problem.
u4ick
u4ick wrote:

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It's a very complicated situation. It depends on the shower head design. The length of pipe, any restrictions, and any type and size of shutoffs in the line.
My best guess: NO.
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