# [Bldg-sim] Indoor pool evaporation rate

Shaun Martin smartin at shaunmartinconsulting.com
Fri Jun 6 09:24:13 PDT 2014

```Hi Rohini,

Here are some quick and dirty formulas:

Unoccupied Pool Evaporation

E0 = ( ( Ap * (95 + 0.425v) ) / ifg ) * (Pw - Pa)

Source: ASHRAE 1989 HVAC Chap 20 Eq 1

Occupied Pool Evaporation

Source: Shah, HPAC, Mar 04

If (A/N) is greater than 500, then:

E = E0 * (160 * N / A + 1)

If (A/N) is between 50 and 500, then:

E = E0 * (62.9 * N / A + 1.2)

If (A/N) is less than 50, then:

E = E0 * 2.5

A = Surface area of pool, ft2

N = Number of pool occupants

E0 = Rate of evaporation from unoccupied pool, lb/hr

E = Rate of evaporation at actual occupancy, lb/hr

ifg = Latent heat of vaporization of water, Btu/lb

p = Partial pressure of water in air, in. Hg.

∆p = (pw – pr), in. Hg.

v = Velocity of air parallel to water surface, feet per minute

Pa = Saturation pressure at room temperature and humidity

Pw = Saturation pressure at water-surface temperature

I agree with Jeff about usage and leaks.  Some other sources of use that are significant:

1. Showers, of course, will be the largest user, up to 60% of all heated water

2. backwash, 4%

3. pool refill – in the pools I was working at, whirlpool and teach pool (young kids) refills were quite frequent, as often as 1-2x per week, the main pool typically once per year, 11-12%

4. cleaning, 3%

Evaporation roughly 20%.

This was for pools built in the 70’s-90’s.

Shaun

Shaun Martin LEED AP

Principal

Shaun Martin Consulting

2060 Pine Street

Vancouver, BC V6J 4P8

P: 604-789-1095

E: smartin at shaunmartinconsulting.com

From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jeff Haberl
Sent: Friday, June 06, 2014 8:23 AM
To: R B; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Indoor pool evaporation rate

Hello Rohini,

One rather dated study that had measured daily amounts over an 18 month period is the study of the Rec Center at the University of Colorado:

Haberl, J., Claridge, D. 1987. “An Expert System for Building Energy Consumption Analysis: Prototype Results,” ASHRAE Transactions-Research, Vol. 93, Pt. 1, pp. 979 - 998 ESL-PA-87-07-01 (July).

In this study we found that the day-to-day evaporation rates were small compared to the amount of water that got splashed out of the pool (i.e., usage).

There also was a relationship between the evaporation rate and the exterior conditions, which caused condensation on the interior of the large window exposure surrounding the pool.

The study also found that there was a large leak in the pool underneath the surge tank, caused by the corrosion of the cast iron drain pipe that was 30+ times more than the evaporation rate. This was confirmed by sampling for chlorine in wet, swampy area directly downhill from the Recreation Center, which was wet because of the 25,000 gallons per day pool leak. Pool filling procedures were also modified to cut the heating energy use by 1/2 in the spring when the pools were drained, cleaned and refilled.

Jeff

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Jeff S. Haberl, Ph.D.,P.E.inactive,FASHRAE,FIBPSA,......jhaberl at tamu.edu <mailto:........jhaberl at tamu.edu>
Professor........................................................................Office Ph: 979-845-6507
Department of Architecture............................................Lab Ph:979-845-6065
Energy Systems Laboratory...........................................FAX: 979-862-2457
Texas A&M University...................................................77843-3581
College Station, Texas, USA, 77843..............................URL:www.esl.tamu.edu
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_____

From: Bldg-sim [bldg-sim-bounces at lists.onebuilding.org] on behalf of R B [slv3sat at gmail.com]
Sent: Friday, June 06, 2014 10:08 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Indoor pool evaporation rate

Hi All,

I am working on calibrating a recreation center model and was wondering if folks had a favorite formula to calculate the evaporation rate from an indoor pool. I am getting quite a bit of range in the lbs/hr evaporated based on different studies/calculators.

Thanks in advance and have a good weekend.

-Rohini

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