Dead ends and Legionnaires?

ChrisJ

Hi all,

We're currently doing a lot of repiping and have a few walls open.

While doing this I want to run a return for my domestic hot water from the second floor bathroom but it would just be a 10' long plugged 3/4" run of pex for a long time. Maybe forever.

It's just in case I ever get the time to do recirculating hot water and since it's in a wall now's the time to do it.

Is this asking for something really bad?

Jamie Hall

I wouldn't think so, @ChrisJ . Just when you do hook it up, flush it well!

Larry Weingarten

Hi, I'd see if there was a way to put a shut off valve at the beginning of the run to minimize the dead leg.

Yours, Larry

ChrisJ

> @Larry Weingarten said:
> Hi, I'd see if there was a way to put a shut off valve at the beginning of the run to minimize the dead leg.
>
> Yours, Larry

Hi Larry,

I thought about that but it's going to be in a drywalled ceiling so no dice.

Larry Weingarten

Hi, Can't use one of those beautiful hatches?

Yours, Larry

ChrisJ

> @Larry Weingarten said:
> (Image)
>
>
> Hi, Can't use one of those beautiful hatches?
>
> Yours, Larry

Are you married @Larry Weingarten ?

Actually, we were considering doing a dropped ceiling for this reason as well as I want access to the tub drain etc.

I don't like how they look but at the same time I don't like loosing all access to everything below the second floor bathroom.

ratio

Not all lay-in ceiling tiles are ugly. Some look pretty good; I'm especially fond of the stamped tin ones. They are not, unfortunately, cheap. Another (expensive but) durable & unobtrusive tile is the drywall squares used in commercial kitchens.

Solid_Fuel_Man

Just build yourself some type of hidden access. I built my own house and let me say there are a few "hidden access points" for cooler things than a valve!

ChrisJ

> @Solid_Fuel_Man said:
> Just build yourself some type of hidden access. I built my own house and let me say there are a few "hidden access points" for cooler things than a valve!

Gladly.

Any suggestions?

Solid_Fuel_Man

Will it be buried in a wall or floor?

I assume wall, will it be close to your shower faucet? Can you put it under a false bottom shelf or cabinet?

ChrisJ

> @Solid_Fuel_Man said:
> Will it be buried in a wall or floor?
>
> I assume wall, will it be close to your shower faucet? Can you put it under a false bottom shelf or cabinet?

Drywalled ceiling under the second floor bathroom. Second floor bathroom has tile floor.

We gutted the first floor bathroom which is where the work is being done.

The plugged end would be in the crawl space under the first floor bathroom.

hot_rod

can you make a loop so it could be circulated?

This German company builds a Venturi fitting to induce flow in loops that are not used daily

https://www.kemper-olpe.de/fileadmin/contents/kemper/pdf/KHS_EN_02_13.pdf

ChrisJ

hot_rod said:

can you make a loop so it could be circulated?



This German company builds a Venturi fitting to induce flow in loops that are not used daily



https://www.kemper-olpe.de/fileadmin/contents/kemper/pdf/KHS_EN_02_13.pdf

After mulling it over and looking at options, I may have come up with an idea which would make the dead end only a foot long or so.

JUGHNE

Chris, do you have access to the bottom of your lav sink?
I connected my recir line there and have a stop valve on it.
Gravity recir to bottom of water heater tank only one floor down. Works great, instant hot water water in the shower with no pump involved.
Search the wall for "Gravity recirculation". There is a Dec 2018 posting with many details.

HomerJSmith

Gee. It's hard to say. 90 deg to 120 deg is an ideal breeding ground for the bacteria. Dead legs are of course in that range for the hot water line. I always try and avoid dead legs. As far as the circulation of hot water in a DHW line goes, new piping will be scrubbed to some extent with circulation. However, heated chlorinated water will break down the the piping barrier in all pipes allowing over time, places where bacteria could lodge. Water hardness and mineralization of the interior could, I would think, provide niches for bacteria to congregate, too.

ChrisJ

> @HomerJSmith said:
> Gee. It's hard to say. 90 deg to 120 deg is an ideal breeding ground for the bacteria. Dead legs are of course in that range for the hot water line. I always try and avoid dead legs. As far as the circulation of hot water in a DHW line goes, new piping will be scrubbed to some extent with circulation. However, heated chlorinated water will break down the the piping barrier in all pipes allowing over time, places where bacteria could lodge. Water hardness and mineralization of the interior could, I would think, provide niches for bacteria to congregate, too.

New piping will be scrubbed But chlorinated water will break down the piping barrier? Huh?

HomerJSmith

Chrisj, to clarify your huh?, what I meant was that new pipe is much smoother inside and therefore the bacteria has less to cling to and can be more easily washed away. Hot chlorinated water breaks down the barrier layer on the inside of the tube, allowing the bacteria something to cling to. The piping that most resists this breakdown is CPVC as I understand it.

ChrisJ

> @HomerJSmith said:
> Chrisj, to clarify your huh?, what I meant was that new pipe is much smoother inside and therefore the bacteria has less to cling to and can be more easily washed away. Hot chlorinated water breaks down the barrier layer on the inside of the tube, allowing the bacteria something to cling to. The piping that most resists this breakdown is CPVC as I understand it.

Ah I see.
That makes sense.