newly built 0.35 lav and loooong time to get hot water

emily reese moody

Sustainability Director, Certifications & Compliance

Jacobs

LEEDuser Expert

469 thumbs up

March 24, 2022

Hi all,

We have a newly constructed, core/shell project having some hot water issues in the core restrooms.

There is a 0.35 Toto lav installed throughout. The hot water heaters are adjacent on each floor, located in the janitor closets. We did the math, and there could be a gallon of water standing and cooling in the pipe between the HWH and the faucets (i.e. over the weekend), and that would take ~3+ minutes to run out at 0.35 GPM.

The tenants are complaining about how long it takes the water in the lavs to get hot. Unconfirmed report is that it takes 14 minutes of flow to get hot water in the early morning. Blame is being thrown around to…wait for it…those "LEED faucets".

Something else may be going on here (that's our hope), but the client is thinking about adding electric POS heaters under the lavs to make the tenant complaints stop. It seems sad to us that we propose to consume more energy to reheat water that was one heated and then cooled in the pipes. Given that nearly every new project uses 0.35 lavs these days, and we have not heard of this issue coming elsewhere, that surely there must be something else happening. Admittedly, we have had several instances where our engineering team did not appreciate how some new element (like a lower flow faucet, or a condensing modular boiler) could upset a conventional design approach. We are wondering if lower flow faucets just require a different approach to hot water heating such as a POS heater or recirculator and we missed it; maybe lower flow faucets just require a different approach to hot water heating, such as a POS heater or recirculator, though this also doesn't seem right, and is counter to what the Googles tell me. The contractor, subcontractor, and Cx agent have all proven useless for this issue, and just throw the A/E under the bus. The owner just wants hot water.

Any insight here would be appreciated.
Disclaimer: I cannot pretend to be a plumbing engineer, but can relay info like a pro.

Post a reply

Mike Fowler

Sustainability Integration Leader, Associate Principal

MITHUN

LEEDuser Basic Member

1 thumbs up

Thu, 03/24/2022 - 22:56

Hi Emily,
Is there any insulation on the hot water pipe? Our local code has pipes with 105-140 degree temp water to have 1" thick insulation on pipes up to 1 1/2" diameter and 1.5" thick insulation on pipes larger than 1 1/2".
Thanks,
Mike

Heather DeGrella

Sustainable Design Director, Associate Principal

Opsis Architecture

LEEDuser Premium Member

54 thumbs up

Fri, 03/25/2022 - 15:48

Something else to throw in the mix, we have been discussing with clients the need for hot water at all for public restrooms. Studies have proven that hot water is no better for removing germs than cold water, so the decision is no longer an issue of hygiene but rather one of personal comfort. That said, from personal experience I am more likely to wash for 20 seconds if my hands are comfortable not cold, so the idea of non-tempered cold water is pretty off-putting to me. Is there an approach that delivers warm - not hot - water that also saves energy and water? Heather DeGrella AIA, LEED AP BD+C, Fitwel Ambassador, EAC-PS, | (she / her / hers) Associate Principal | Sustainable Design Director [cid:opsislogo2021_13a53c65-c652-4f53-a86d-657f2f0f9b85.png] Architecture, Interiors & Planning 920 NW 17th Avenue, Portland, OR 97209 o 503.525.9511 d 503.943.6228 w opsisarch.com

emily reese moody

Sustainability Director, Certifications & Compliance

Jacobs

LEEDuser Expert

469 thumbs up

Thu, 03/31/2022 - 23:42

Slight update from our side: We looked around at some other projects designed by our consulting engineers, and the recirculation line/pump seems to be the common solution. If we understand all this correctly, a recirculation line/pump is required by code for long(er) runs from the water heater. In our situation, we do not exceed that max length, but ours is still long enough that the water is cooling enough standing in the pipe (even with the correct HWH temp and insulation). We also believe there's a potential influence from the winter aspect being in the NE, either from the temps, themselves, or people's perception of everything being colder. I do remember living there and freezing my teeth every morning when brushing with the subzero water coming from the taps, so I can believe at least a slight influence from ambient temps around the pipes, even with insulation. Only other insight we got was to check the thermostatic mixing valve at the faucet, itself, too.