Old plumber wisdom, is he right or not?

  • Thread starter Thread starter Jonathan212
  • Start date Start date
Click For Summary

Discussion Overview

The discussion revolves around the claim made by an old plumber regarding the pressure characteristics of 1/2'' versus 3/4'' piping. Participants explore the implications of pipe diameter on pressure and flow, considering both theoretical and practical perspectives. The conversation includes technical reasoning, anecdotal experiences, and challenges to the plumber's assertion.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that a smaller diameter pipe may lead to higher exit speed, which could be perceived as higher pressure, despite lower flow rates.
  • Others argue that a smaller diameter pipe results in a higher pressure drop for the same flow, questioning the plumber's assertion.
  • A participant proposes that the plumber might be considering practical pressure from a homeowner's perspective, where perceived pressure can differ from technical measurements.
  • There is mention of the need to clarify where pressure is measured in the system, as this can influence the interpretation of the plumber's statement.
  • Some participants discuss the concept of residual pressure tests used by plumbers, which may contribute to their perceptions of pressure in different pipe sizes.
  • One participant raises the idea that the plumber's claim could be consistent if the input pressures for both pipe sizes are not the same.
  • Technical calculations are proposed to analyze the relationship between input pressure, flow rates, and pipe sizes, leading to further exploration of the conditions under which the plumber's claim could hold true.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the plumber's claim. Multiple competing views remain regarding the relationship between pipe diameter, pressure, and flow, with some supporting the plumber's perspective and others challenging it.

Contextual Notes

Participants note that the discussion is influenced by assumptions about where pressure is measured and the conditions of flow. There are unresolved mathematical relationships and dependencies on definitions of pressure and flow characteristics.

Who May Find This Useful

Individuals interested in plumbing, fluid dynamics, and the practical applications of pressure in piping systems may find this discussion relevant.

  • #31
Let us not forget the plumber's claim is about pressure, not flow rate. Pressure at the point where his piping ends and devices begin. We still care about flow so we might as well ignore him, even if when he is right.
 
Last edited:
Engineering news on Phys.org
  • #32
The problem here, as in so many, many cases, is not in the pursuit of the answer but the question.
The OP said, the old plumber said ‘this size [1/2”] would give a HIGHER pressure compared to the 3/4'' option’.

Of course, there is almost no information to work with here and moreover the old plumber’s statement is an
informal logical fallacy
(wrong but not absolutely, self evidently wrong).

However, it is pretty darn close to being a formal logical fallacy and it might help to explain this to your plumber :smile:

Then again...
 
  • #33
Bee Tree said:
[. . .]
Many plumbers have trouble with the meanings of pressure and flow. To be an old plumber now, he may well have gone into plumbing because he wasn't getting good grades... and never understood quite a lot of things, very well.
[. . .]
I had to chuckle. :smile: My husband is a Union plumber and pipe fitter. He knows his stuff. He is now retired but still fixes every thing at our home and helps his friends too.:wink:
 
  • #34
Mary Conrads Sanburn said:
My husband is a Union plumber and pipe fitter.
How do you tell a plumber from a physicist?

Ask them to say "unionized".
 
  • Informative
Likes   Reactions: hutchphd

Similar threads

How does it take a lot of skill to be a good plumber?
  • · Replies 59 ·
2
Replies
59
Views
16K
Implausible multiple failures in my gas central heating system
  • · Replies 9 ·
Replies
9
Views
2K
HVAC Ideas for reducing home boiler PSI
  • · Replies 27 ·
Replies
27
Views
4K
Closed vs. Open Crawlspace & Automatic Vents vs. Dehumidifer?
  • · Replies 10 ·
Replies
10
Views
3K
Science of Evaporation - General & Personal Questions
  • · Replies 23 ·
Replies
23
Views
3K
Time to empty gas cylinder (problem worked, but would like feedback)
  • · Replies 7 ·
Replies
7
Views
4K
Undergrad Are Plumber Blocks Strong Enough for 880 Nm of Torque?
  • · Replies 9 ·
Replies
9
Views
9K
Other Advice for Pursuing Physics: My Friend's Story
  • · Replies 2 ·
Replies
2
Views
2K
Plumbing Compressed air powered water pressure
  • · Replies 39 ·
2
Replies
39
Views
15K
Newbie questions about the NEC code and flexible "dry use" metal conduit
  • · Replies 16 ·
Replies
16
Views
4K