Will a pressure booster pump improve volume with galvanized pipes?

[Allthumbs2]

I have a large three-story house with old corroded galvanized pipes. The main line comes in at the lowest of the three levels.

Some of the fixtures have fine volume but many do not. The water pressure is about 40 PSI when checked at a hose bib. I realize the difference between volume and pressure.

Would adding a pressure booster pump help the fixtures that have low volume because of the corroded pipes?

The line coming in from the street is 3/4” copper. I could put the booster prior to the start of the corroded galvanized, so the booster would get plenty of supply volume. I would not even be asking this question, if I did not have this situation where I could supply the booster pump a full volume of water.

I am wondering if it might be a relatively inexpensive/simple way to possibly get more volume at the problem fixtures like a shower. What are your thoughts?

 

[LLigetfa]

The answer is "it depends". Pressure/volume loss is due to friction and friction loss is commensurate with volume so while more pressure creates more volume, more volume creates more friction.

 

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[John Gayewski]

Yes you would get more. What are you getting through the shower head right now? Measure with a bucket and see what you get vs what the shower head says you should get.

 

[wwhitney]

Best case back of the envelope:

Let's that your problem fixture is 23' above where you measured 40 psi (3rd floor bathroom), which means a 10 psi pressure loss just due to elevation. Let's say that your rusty galvanized pipe is the limiting factor and controls the flow rate.

Then if you install a booster pump to go from 40 psi to 70 psi, after subtracting the 10 psi elevation loss, you've doubled the pressure available for the fixture and for getting through your rusty galvanized pipe. For pipes, flow rate Q varies with pressure P as approximately P^1.85 (I think P^2 is an idealization answer). So by doubling the pressure, you'll get at most 2^(1/1.85) = 1.45 times the flow. I.e. a 45% improvement.

I believe that's a best case answer, as everything about the physics I'm ignoring would on balance make it less effective. Not 100% sure on that.

In the long term, the galvanized pipes will need to be replaced, so it's worth considering whether doing it now would be better than just applying a band-aid.

Cheers, Wayne