What is "head" and what isn't "head"

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System A could cause air to be drawn down the vent pipe during high demand. System B is the correct way.
Jeff
 
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You don't need them equations. They don't apply. You don't have perfect pipes. You DO need the experience to know what works, and maybe a few charts, once in a blue moon. It's a garden tap not a chemical pipeline.
So, sure a tad of common sense and simple science, but more importantly, whether burrs on pipes, or stopcocks, or gate valves, or bends, or the regulation check valve, actually affect whether it'll work WELL ENOUGH that the plumber gets paid!.

I'm sure they do apply but you are quite right, you DO need the experience too. However, when the system you install DOESN'T work, even after 35 years experience, you need to know the theory behind it all too.
Again, I don't profess to know but I'm learning rapidly after my experiences with the plumber.
 
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System A could cause air to be drawn down the vent pipe during high demand. System B is the correct way.
Jeff

Interesting.... Would it work if the cold feed was 22mm and the vent say 8mm

Have you any thoughts of a way around it Jeff. Is it possible/acceptable to put a non return valve on the vent pipe?
 
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This reminds me of a new home I worked on years ago. It was a very rural location with a Private water supply. The Architect for whom the house was being built, was from the 'Plumbing is easy' brigade. He'd buried about 2 Miles of 25mm MDPE pipe from the elevated 60M high water tank to his new home. He was very, very disappointed when his Water flow rate was so pizz poor it hardly would flow out the pipe!!

Never confuse pressure & flow.
 
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This reminds me of a new home I worked on years ago. It was a very rural location with a Private water supply. The Architect for whom the house was being built, was from the 'Plumbing is easy' brigade. He'd buried about 2 Miles of 25mm MDPE pipe from the elevated 60M high water tank to his new home. He was very, very disappointed when his Water flow rate was so pizz poor it hardly would flow out the pipe!!

Never confuse pressure & flow.

This is another occasion where he should have known how to apply the Darcy-Weisbach equation.

This guy seems to know what he is talking about:-
http://www.johnhearfield.com/Water/Water_in_pipes2.htm
 
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We have the Jennings Heating equation to consider too:


Good pressure = nice shower + moderate ear bending from missus / ∆U(slow filling bath)+ (P(A ∩ B)undersized pipe work)


This equation works in conjunction with a subset:

Good Flow = fast fill bath + moderate ear bending from missus / ∆U(pants shower performance)



All this however, is a loosing battle due to the following:

Universal constant of ear bending from SWMBO as it is a genetic predisposition.


Also:

Champagne Ideas / Beer Money = Shyte ablutionary execution.



* edit - sorry had a bracket in the wrong p[lace on the probability equation. I have often wondered if that should be a delta as well as the "potential"


hhhmmm.
 
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System A could cause air to be drawn down the vent pipe during high demand. System B is the correct way.
Jeff

Interesting.... Would it work if the cold feed was 22mm and the vent say 8mm

Have you any thoughts of a way around it Jeff. Is it possible/acceptable to put a non return valve on the vent pipe?

Nope. You haven't shown a vent anyway and it should be unobstructed to the cistern. If the draw on a tap below the cylinder exceeds that which the cold feed can supply air will be drawn into the outgoing hot from a vent if it were located where it should be. You'll get spluttering at the hot tap especially if they were decent 3/4" bath taps. Minimum vent diam is 19mm according to Mr. Prescott.
 
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This reminds me of a new home I worked on years ago. It was a very rural location with a Private water supply. The Architect for whom the house was being built, was from the 'Plumbing is easy' brigade. He'd buried about 2 Miles of 25mm MDPE pipe from the elevated 60M high water tank to his new home. He was very, very disappointed when his Water flow rate was so pizz poor it hardly would flow out the pipe!!

Never confuse pressure & flow.

This is another occasion where he should have known how to apply the Darcy-Weisbach equation.

This guy seems to know what he is talking about:-
http://www.johnhearfield.com/Water/Water_in_pipes2.htm[/QUOTE]

No, Darcy-Weisbach equation is pressure!! You're getting the two mixed up fella!!
 
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System A could cause air to be drawn down the vent pipe during high demand. System B is the correct way.
Jeff

Interesting.... Would it work if the cold feed was 22mm and the vent say 8mm

Have you any thoughts of a way around it Jeff. Is it possible/acceptable to put a non return valve on the vent pipe?

Nope. You haven't shown a vent anyway and it should be unobstructed to the cistern. If the draw on a tap below the cylinder exceeds that which the cold feed can supply air will be drawn into the outgoing hot from a vent if it were located where it should be. You'll get spluttering at the hot tap especially if they were decent 3/4" bath taps. Minimum vent diam is 19mm according to Mr. Prescott.

What John, the Labour fat f.ck??!!!
 
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No, Darcy-Weisbach equation is pressure!! You're getting the two mixed up fella!![/quote]

That's why I would never make a plumber.. ! :)
 
L

longdogs


No, Darcy-Weisbach equation is pressure!! You're getting the two mixed up fella!!

That's why I would never make a plumber.. ! :)[/quote]

Excellent on Google though. Do you test your GP when you visit him :LOL:
 
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No, Darcy-Weisbach equation is pressure!! You're getting the two mixed up fella!!

That's why I would never make a plumber.. ! :)

Excellent on Google though. Do you test your GP when you visit him :LOL:[/quote]

If I had cause to I would... Never accept anything you are told, or read, as gospel... Get a second opinion.
From the positive feedback I have got on here it proves the advice I got from the plumber was wrong.... and I won't be employing him... simplz. :D
 
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image_29.jpg


You don't want to do it like that.....
 

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