Given an orifice rated 1.8 GPM of water at 90 PSI, how do I calculate the flow rate at 30 PSI and what rating I would need to purchase to achieve 1.8 GPM at 30 PSI?
Below added to give some context, based on responses. Sorry, as a programmer I always reduce problems to the simplest form. Apparently, that's a bad thing on this site.
I'm trying to fix the shower in my new apartment in Chicago. The building owner says that as long as warm water comes out she has met her legal requirement. Google seems to agree with her. I've added "check shower, sinks, etc." to my apt inspection checklist for my next move, but that doesn't help me now. I should probably Google "apt inspection checklist" next time to see what else I should have looked at.
I don't know if the problem is in the pipes, values, showerhead, or what. The sink works a lot better now that I removed the 2.2 GPM aerator. Changing the showerhead would be the equivalent for a shower, but simply removing it doesn't let you see if that fixes the problem like removing an aerator does. I'm guessing flow rate is proportional to pressure, but I don't know if it is a major or minor effect.
The showerhead is labeled 1.8GPM, which seems to be fairly normal for a showerhead. I used a Watts gauge with an aerator adapter on the sink to find my water pressure. I spoke with the showerhead manufacturer (Waterpik) and they stated that they rate their showerheads based on 90 PSI. They were unable to tell me how well they would work at 30 PSI. Seems like a scam to me. Who has 90 PSI water pressure?!?!
All the formulas I find on the Internet require all kinds of other information I don't have and are just too complex for me to figure out.