Time For Hot Water To Reach A Fixture

noahweb

Is there a time frame that is considered appropriate for allowing hot water to reach a fixture? Any standards from organizations? Is 2 minutes acceptable?

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KillerToiletSpider

What is the lineal footage of the fixture from the hot water source, the pipe size, and the incoming water pressure?

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Tinstaafl

Valid questions for analysis of a problem, whether real or perceived--but not actually responsive to the intent of the OP.

I'll admit to some curiosity on my own part. I've never seen a published standard for this.

Leo G

I think anything past 15 seconds is too long. I wouldn't tolerate 2 minutes.

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j_builder

I agree with KTS to many?'s along with are the hot lines piped in galvi/copper/pex? insulated? sizes of tank water heater/tankless/heat pump/solar? 2 minutes I'd be boiling water faster or sending the kids next door to tap off there waterheater.

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greg24k

I agree with Leo, 2 minutes is way to long...there is a problem if it takes that long.

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Leo G

Trying to figure it out. I think a 1/2" pipe 98 ft long will hold 1 gallon of water. Most systems will deliver about 6 gallons per minute. That means that the water has traveled 588' per minute. In 15 seconds the water should be able to travel 147'. So 2 minutes of wait time the pipe would need to be over 1000' long.

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thom

Unless the pipe is buried in earth and not insulated in which case, the earth may need warming also. Then, the time would depend on how rapidly the earth would pull the heat from the pipe and that's a function of the soil and the moisture in it.

Some pipes buried in earth just won't heat up. About all you can do is disconnect the pipe and use the cold with an electric point of use flash heater.

Mellison

I just had a customer complain that it took quite long for the hot water to reach her bathroom which was on the fifth floor.
She just bought the apartment and remembered the past occopant refer to the long waite. I also tested it, and it took a good 5-7 minutes.
I found the return in the basement and disconnected the union. The vertical return shook like a branch in a wind storm.
I had my plumber come out to find where it had been terminated. I turns out it was capped between the fourth and fifth floor floor joists by some shmo who had no idea what it was. Or did know and didn't care.
(I knew I should have taken a picture) My plumber reconnected the return to the riser,installed a circulator pump and know the problem is solved.
Not exactly following the thread here but I thought the plumbers here would get a kick.

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noahweb

I do not know all of the specifics.

It is on the 21st floor of a highrise which has hot water supplied through a recirculating pump.

I'm not a plumber. But I believe 1/2" copper. Non insulated. Coming from building core.

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greg24k

Thom, why would anyone send hot water through a pipe buried in earth? I never heard that. There is always a cold water supply to a home and to a water heater or other heating source, which will heat the water and from there hot water will travel to places it needs to go.
Most plumbers will suggest a circulating pump installed to supply hot water faster based on special circumstances so the is no wait time.i,e big homes, water supply must pass through unheated spaces, bathroom is being far away from the heating source etc.

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Tom M

6 Gallons/min? From where? Silcocks or toilets maybe but they dont carry hot water which leaves a shower head @2.5 gpm. All comes to the run length or fixture demand.

Leo G

You must be a good boy. I took my water restrictor out of my shower head the day I purchased it.

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thom

It's the normal way to do it in a single story on a slab. Even on two stories with a slab the plumbers like to run the supplies underground. I insist they run the supplies between floors but on single stories, there is no other way to do it.

Some (only a few) will wrap the buried hot water pipes in insulation.

KillerToiletSpider

Tell the building engineer there is a problem.

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greg24k

I did an addition a while back, it was a 800SF addition with a crawl space not a slab. The plumber who was doing the job, ran water lines up the original wall of the house and ran all water lines in the ceiling joists 2" above the sheetrock ceiling, insulated them and R-30 insulation was done right above the lines. He said he rather put them in the ceiling then crawl space, less likely they will freeze. He did add main shut off valve in the basement, incase they leave on vacation, to close the water off just incase. We had some cold winters since then and there was never a problem or any call backs from them.
I am just wondering if anyone else would do that, or finds this way as a better way of doing it, other then run pipes in the crawl space.

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thom

I've done it that way. It's a challenge getting the plumbers to do anything different than they normally do. They have a million reasons why it won't work.

The pipe wrap isn't necessary as long as the insulation goes completely above the pipe. That puts the pipe on the heated side of the envelope. Of course that means the insulators must have a measurable IQ and that certainly isn't a given.

greg24k

I think you would need insulation around the pipe for 2 reasons, one is to provide extra insulation in the winter and the other reason, incase condensation builds up on the pipe it will not drip directly on to the sheetrock.

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