Plumbing theory


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Old 04-09-06, 10:35 AM
J
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Plumbing theory

I'm looking to do some major plumbing work in my house this summer - replacing most of the supply pipes, both hot and cold, since the current ones are mostly galv. In the process, I'm going to reroute some of them so as to make things simpler (the house is almost 80 years old, and much of the plumbing was by accretion).

I'm wondering if there is any engineering theory I should be aware of that affects how the pipe layouts should be designed. Is there a good book on this? I don't mean something on how to sweat pipe and connect fixtures, I means how to design an efficient distribution system for the water to flow through, and any computations that must be made.

Thanks,
Juliean.
 
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Old 04-09-06, 11:38 AM
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> how to design an efficient distribution system for the water to flow through,

The main thing is having the water heater as close to major points of use as possible.

> and any computations that must be made.
Diameter of the pipe needed depends on what the fixtures consume, how long the run is, and the supply pressure.

In general, your options inside a house are 3/4" and 1/2".
Rarely is 1" needed other than the entrance before it splits to hot and cold.

A general rule of thumb is that 3/4" is used for distribution and 1/2" for branches to each room.

The theory is that there is less wear and tear on your plumbing fixtures the slower the water is moving.
The larger the diameter, the slower the water moves.
The trade-off (which I consider to be a big deal) is that a bigger pipe wastes a lot more energy heating water that doesn't need to be heated - both hot and cold, and just plain wastes water when you let the tap run while waiting for hot or cold water.
 
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Old 04-09-06, 02:19 PM
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Well, the entrance pipe is 3/4", so I really see no reason to go bigger.

The position of the water heater is fixed, but it's pretty close to everything. I was going to just run 3/4" pipe everywhere, is that a bad idea? Should I drop down to 1/2" for the terminal branches?
 
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Old 04-09-06, 03:21 PM
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Originally Posted by jgalak
the entrance pipe is 3/4", so I really see no reason to go bigger.
Neither do I.


> I was going to just run 3/4" pipe everywhere, is that a bad idea?
I think so.

> Should I drop down to 1/2" for the terminal branches?
I always do. I use 1/2" everywhere except where something bigger is needed.

Do you have any idea how long you have to wait for hot water to come through a 3/4" line to a bathroom sink?
 
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Old 04-09-06, 05:23 PM
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"I'm wondering if there is any engineering theory I should be aware"

With apologies to JGalak in advance.....

Many years ago a friend ( an "A ganger" - a submarine service equivalent of a plumber, among other things) told me that there are only two things that you need to know to be successful as a plumber. S*^% floats and water runs downhill. Any other theories are simply corrolaries of these two scientifically proven facts.
 
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Old 04-10-06, 01:49 PM
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Water filters

Another question - I have seen "whole house" water filters in the local Big Box stores, and I'm wondering whether they are a good idea or not. I filter my drinking water (Brita), and am planning on putting in a filtered water tap by the kitchen faucet, but I'm thinking about the whole house filters, primarily so that the shower water doesn't taste bad.

The water isn't terrible, but it's not very pleasant. My real concern is whether the filter will cause a drop in the water pressure - I like high water pressure in the faucets and shower, and don't want to lose it. If it does cause a significant pressure drop, would placing two or three filters in parallel help with that?

Also, where in the system should this be placed? Right on the inlet pipe? On the cold side only (after the split off to the water heater)? Does it matter if the boiler feed gets filtered? It seems to me that putting it right on the inlet pipe, before it splits up would work best as it would help keep the water heater and boiler clean as well.
 
 

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