# Homework Help: Head loss in parallel pipes

1. Nov 12, 2012

### zzinfinity

1. The problem statement, all variables and given/known data
I have three valve/coil systems connected in parallel as shown in the attached figure. If I know the head loss of each valve/coil is 40 feet, can I add them in parallel like you do with resistors in circuits?
Thanks!

2. Relevant equations

1/h=1/h1+1/h2+1/h3 (possibly)

3. The attempt at a solution

2. Nov 13, 2012

### CWatters

You forgot the diagram.

Not my field but I believe you are incorrect. Isn't head drop equivalent to "voltage drop"? In which case consider what happens when you connect three resistors in parallel... the current flowing in each changes until they end up sharing a common voltage drop (head drop).

Only _if_ the head drop was the same on each leg could you easily add them in parallel. In that I believe case you get h = h1 = h2 = h3. This is equivalent to adding three identical resistors in parallel.

If the head loss is different for each leg... Do you know the resistance of each leg ? eg the head loss per unit of flow?