“I told you so!” – was coming to my mind while looking at the plumbing in a Swedish single family home built sometime in the 1970’s.
Some plumbing lines were partially exposed to keep them in the interior conditioned space. What caught my eye right away was a 3/8 inch branch (or twig) coming off of a 3/4 inch trunk line.
The use of 3/8 inch plumbing lines (or twigs) fits right with the material and energy conservation goals of an efficient domestic hot water delivery system, as was explained to me by the hot water guru Gary Klein. The problem for us in Chicago is that the smallest allowed pipe diameter per plumbing code is 1/2 inch. The rationale behind this limitation is, so I assume, concerns about pressure drop and insufficient flow capacity. But it also puts a limit on the efficiency of our hot water delivery system.
Seeing that a built 3/8 inch twig line didn’t cause the world to implode was rather exciting. Not only that, but the 3/8 inch cold water line services three fixtures: 1) the toilet, 2) a sink, and 3) a shower, while the ? inch hot water line only serviced the sink and the shower.
The structured plumbing system that I have described in a previous post, recommends the use of 3/8 inch twigs. But each twig should just service a single plumbing fixture, not multiple fixtures.
Serving three fixtures with cold water and two fixtures with hot water using a 3/8 inch twig lines would take us – so one could argue – into deep water. That begs the question: Why would several fixtures on one twig be acceptable?
The bathroom in the Swedish single family home is meant to be used by a single person at a time. In other words, you shouldn’t need to worry about somebody flushing the toilet or using the sink while you take a shower.
And I used that shower. There was no problem with the water flow rate or the water pressure, despite the nine feet long 3/8 inch twig. And being the nerd I am, I let the shower run while flushing the toilet or turning on the sink faucet. There was a very brief but minor pulse in the shower’s water flow, but other than that, no detectable flow reduction or pressure loss.
For full disclosure, I should mention that the bathroom in question was on the 1st floor and only a few feet away from the water heater and water main. The second floor bathroom has a different set up. Here a 1/2 inch twigs (or branches) services the various plumbing fixtures, probably to mitigate pressure loss that may come with the elevation and friction that comes with the longer pipe run.
Now – is that 3/8 inch twig I observed an exception? Apparently not. I noticed almost the exact same setup in a restaurant men’s room — a 3/8 inch twig servicing all fixtures.
As unscientific and nerdy as this is, I am delighted to see proof that 3/8 inch twigs can work and can be safe. But to whom can I take my “I told you so?”
- Plumbing – material conservation
- Plumbing – energy conservation (part 1)
- Plumbing – energy conservation (part 2)