Water pressure and pipe size ?

[Daffy D]

Having a discussion the other day about water pressure.

I have a water tank on a tower with 3/4 in pipe running along the back of the house that reduces to 1/2 in as it goes through the wall to feed the various taps and of course the shower.

My reasoning is that the 3/4 reduced to 1/2 in at the last moment before getting to the tap will give more pressure, a bit like holding your finger over the end of a hose pipe.

My friend says having 1/2 in pipe all the way straight from the tank will give more pressure

Any thoughts?

[jvs]

More water in the pipe will give you more pressure because there is more weight behind it,So yes the bigger pipe will give you more pressure.

[MW72]

pressure is not related to the size of the pipe. the larger the pipe the larger the volume of water but pressure is not affected. pressure comes from the energy of the water which in your case this is directly related to the height of the storage tank. if your tank is 10 meters above the outlet you will have 1 bar (14/15 psi) of pressure. for ever 10 meters you raise the tank you will gain 1 bar of pressure. if you don't have enough pressure you should fit a small pressurisation pump in line.

Sent from my KFTT using Thaivisa Connect Thailand mobile app

[MW72]

Arjen beat me to it.

Sent from my KFTT using Thaivisa Connect Thailand mobile app

[NeverSure]

The posts above are right on. You might even "experience" what seems like less pressure with the 1/2 line because of added friction and carrying capacity. There simply might not be enough volume at your shower head.

The idea of "a bit like holding your finger..." is defeated when the water enters the shower head. There it spreads out to fill the shower head and serve all of the spray holes. A larger pipe feeding that will do better.

Edited April 26, 2014 by NeverSure

[IMHO]

What everyone else said.. a larger diameter pipe will support a higher flow rate, which means more water. The problem is, most bathroom fittings are designed with a 1/2" thread, so you can't run 3/4" all the way... but you can get close

We always run a 1" pipe from the pump to around the house, then tee off a 3/4" feed to each room, then reduce to 1/2" at the last possible moment. Garden taps are fed directly with 1" pipe for maximum flow rate.

Edited April 26, 2014 by IMHO

[Daffy D]

I believe that the larger the pipe the better the flow/pressure that's why I have 3/4 in pipe right up to the point where it goes though the wall to the tap.

The reason for my OP was that a couple of people have said I would get better pressure if I used 1/2 in pipe all the way from the tank. One was at the place where we bought a pump and just the other day the guy who came to repair the water tank.

Now I KNOW the smaller pipe will not give better pressure than the bigger pipe but after two people have told me otherwise I was beginning to doubt myself .