# Homework Help: Low Water Pressure in high rise buildings

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1. Jan 9, 2015

### sco_111

• Missing homework template due to originally being posted elsewhere.
Hello, I am learning physics on my own and came across this question about why we would have low water pressure in a high rise apartment compared to an apartment located on ground level. I googled and cannot find a direct explanation.

I took some time to think about the approach and I could only come up with this explanation.
First of all, I assume that the energy used to deliver a fixed amount of water is the same for a low-rise and a high-rise apartment (since water pumps should be working at constant power). Does this assumption make sense?
Secondly, Energy = Force x distance and pressure is proportional to force. Area of taps outlets are the same.
For the same amount of energy, the lowrise apt should receive water at a higher force/pressure as compared to a high rise.
Does that make sense? Anyone has a better explanation?

2. Jan 9, 2015

### Orodruin

Staff Emeritus
No, this assumption is wrong. What is the energy required to move 1 kg of water to the bottom floor? What is the energy required to move 1 kg of water to the top floor?

For a fluid in a connected system, what is the relation between the pressure at different heights?

3. Jan 9, 2015

### sco_111

I would understand that the enrgy required to move 1kg of water to the top flr would be proportionally higher to the height ratio. So, my assumption is incorrect.
This question is part of the Pressure topic and not in fluid dynamics (which I think is advanced). So, I only know about pressure at different heights for a column of water but I think this does not apply here. Any other clues? Thanks.

4. Jan 9, 2015

### Orodruin

Staff Emeritus
Why would it not apply?

5. Jan 9, 2015

### sco_111

For a column of water, the pressure is proportional to the height of the column of water. So, at different heights, h1>h2, P(h1)<P(h2).
So, I should think of this in this way.
If I think of the pump as a water body which is situated at a higher level than the building, then this would apply. Is that correct?

6. Jan 9, 2015

### sco_111

Thanks, orodruin for your help. Apologies for flouting some of the forum rules.