Cooling Tower Water Use – Basic Audit

Cooling Tower General Observations

a) Cooling tower location ___________________________________

b) Tons of cooling capacity (if known) _________________________

c) Are flow meters or submeters present on feedlines (circle one)? YES / NO

d) Are flow meters or submeters present on drainlines (circle one)? YES / NO

e) Is the tower a closed loop (not once through) (circle one)? YES / NO

f) At how many cycles is the tower currently be run at?

(you may have to consult with your maintenance vendor). ________

g) Looking at Table 14, what percentage of total water use would be saved if the cycles of concentration were increased

from the current level to five or six? ________

h) Indicate the visible condition of the cooling tower:

None *Very little Some A lot Where? Noticeable leaks

Noticeable corrosion

Mineral precipitate scaling on the heat exchangers, condenser tubes, or elsewhere

Algae or slime (biofouling)

Drift (misting)

*This would account for a small amount at the interface where the air hits the corrugated heat exchangers, condenser tubes, etc.

Overview of Outdoor Water Use

This section of the guide presents challenges and solutions for improving irrigation efficiency. They can be applied anywhere, but in some cases there are specific ‘call out’ references to certain Florida-based resources. These resources are only supplemental to the general tasks. Similar information should be available for most areas.

For this guide, almost all of the irrigation system and landscaping audit activities fall under the basic level. For these activities, extensive

familiarity with irrigation systems is not required. However, you will need to perform certain procedures while the system is operating. This requires knowledge of how to use the timer or controller to manually engage the system. For assistance, refer to the owner’s guide for the controller or secure the assistance of your facility’s irrigation contractor. Alternatively, some procedures can be conducted during a scheduled irrigation event, but this is recommended only as a last resort.

Box 10. Outdoor Water Use Audit Structure and Recommendations

There are two main points of focus related to auditing outdoor irrigation and landscaping: the irrigation controller/timer and the irrigation zones/stations. The procedures for each of these are as follows:

Irrigation controller/timer

- Irrigation Schedule and Controller – Basic Audit

- Rain/Soil Moisture Sensor – Basic Audit and Advanced Audit

Irrigation zones/stations

- Irrigation System and Landscape Survey – Basic Audit and Advanced Audit

- Irrigation System Distribution Uniformity, Application Rate and Calibration – Basic Audit

In general, you will be investigating the most basic settings of the controller as well as the landscape plantings and irrigation hardware in each zone. Although presented separately for descriptive

purposes, you may be able to perform multiple audit procedures at one time as you survey each zone. For this reason, the irrigation and landscape worksheets have been combined for your convenience in the Irrigation and Landscape Audit Worksheet in Appendix C.

Some of the tasks can be accomplished with greater ease if there are at least two people working together, possibly using two-way radios or cell phones, with one person at the irrigation controller turning each zone on and off and one surveying the landscaped areas one zone at a time.

Irrigation Blueprint or Hand-drawn Sketch

Blueprints of the irrigation system would be helpful when conducting the audit procedures, but are not necessary. If irrigation line blueprints are not available, a simple sketch of the property showing the irrigation zones/stations should be created and used (see page 86).

Considerations for Efficient

Outdoor Irrigation

and Landscaping

Water  for  irrigation  may  come  from  various  sources, including potable and reclaimed water,  self‐supplied  wells,  and  retention  ponds.  Regardless of the source, water should be used  efficiently  and  increasing  efficiency  can  reduce  operating expenses in many cases.  

Water Efficient Irrigation

Irrigation systems are not always necessary, but  in  some  cases  they  are  vital.  When  in  place,  they  should  be  used  in  the  most  efficient  manner  and  employ  the  most  appropriate  water delivery hardware and controllers.   In  all  cases,  an  irrigation  system  should  be  considered as supplemental to natural rain. All  systems  require  monitoring  and  regular  maintenance to continue operating efficiently. 

Water Efficient Landscaping

The  amount  of  irrigation  required  depends  in  part  on  the  landscape  materials  used.  Plants  should  be  selected  according  to  the  local  climate and site‐specific conditions, such as the  soil’s  water  holding  capacity  and  the  available  sun and shade. Once in place, plants should be  managed  and  cared  for  to  most  efficiently  use  water, pesticides, and fertilizers. 

How Much Water Should Be Applied

During an Irrigation Event?

The  objective  of  irrigation  is  to  supplement  natural  rainfall  to  meet  the  planted  material’s  water  needs.  The  correct  amount  or  irrigation  depends on the rate of evapotranspiration (ET),  which  is  the  combination  of  evaporation  from  soil  and  transpiration  from  plants.  ET  is  a  function of the plant species and growth cycle,  humidity, wind, temperature, and soil moisture  (Ramey 2004).   Florida Focus  Figure 10 shows the water needs of a typical South Florida lawn by month due to ET, the actual average monthly  rainfall in Florida over a recent 41‐year period, and the amount of water consequently needed to meet the lawn’s  ET demand. These are averages and your specific site conditions may vary. 

Figure 10. Monthly evapotranspiration (ET) demand, rainfall, 

and supplemental irrigation needs of a typical South Florida lawn. 

Inches

In addition to ET, soil water holding capacity affects how much you should water. The amount of water soil holds depends upon various factors, including soil structure and texture. Sandy soils can hold approximately 1 inch of water in the top 12 inches of soil. Medium textured soils and soils containing clay (fine sandy loam, silt loam, silty clay loam) can hold twice as much water as sandy soils (Table

15) and do not drain nearly as fast. Therefore,

they require less frequent watering.

In general, less frequent, deeper watering is better for plants and more efficient than frequent, shallow watering. For sandy soils, applying ½ to ¾ inches of water will thoroughly wet the root zone and will encourage deeper rooting, which increases drought tolerance (Trenholm et al. 2006).

Excessive watering (beyond ¾ inches in one event) creates soil moisture beyond the turfgrass roots and carries away fertilizers and other agrichemicals.

Table 15. Range of water holding

capacity for different soil textures.

Texture Class Water Holding Capacity _{(inches/foot of soil)}

Coarse sand 0.25 – 0.75

Fine sand 0.75 – 1.00

Sandy loam 1.10 – 1.20

Fine sandy loam 1.25 – 1.40

Silt loam 1.50 – 2.00

Silty clay loam 2.00 – 2.50

Silty clay 1.80 – 2.00

Clay 1.20 – 1.50

Source: Plant & Soil Sciences eLibrary, 2013.

Florida Focus

Many parts of Florida have sandy soils, which can hold approximately 1 inch of water in the top 12 inches of soil. As per the University of Florida’s Institute of Food and Agricultural Sciences (IFAS), irrigation applications should not exceed 0.75 inches of water during an irrigation event (Trenholm et al. 2006). At this rate, one irrigation event per week would equal 3 inches per month and two weekly irrigation events would amount to 6 inches per month.

The nine Florida-Friendly Landscaping Principles provide guidance for efficient landscaping in the state. The principles and related information can be found in A Guide to Florida-Friendly Landscaping by Florida Yards & Neighborhoods.

Computerized irrigation controller

IRRIGATION SCHEDULE AND CONTROLLER – BASIC AUDIT

Background and Description

Automatic irrigation systems operate according to a timer or central controller. A timer runs on a preset schedule that directs water to each zone (sometimes referred to as a “station”) for a specified time. Most central controllers run according to a schedule, although some are governed by climactic factors or on-site moisture conditions. Most work best with electric valves instead of indexing valves.

The improper setting or functioning of an irrigation timer or controller can result in wasting large amounts of water and perhaps put a facility at risk for a fine for irrigating outside of any local watering rules.

Because the controller sets every zone of the system in motion, it is important to become familiar with it. Most controllers have a manual ‘On/Off’ switch that can be used to engage each zone or station of the system. Once you understand how this works, you can begin to investigate the entire system. Even if you are not prepared to make adjustments to the runtimes, it is helpful to know for how many minutes each zone is set to irrigate. This can help you begin to create a mental picture of your facility’s outdoor water use. Most controllers have a dial or a pad that is used to select the settings for each zone or station; some have a key pad with up and down arrows. You should be able to view the settings for each zone by turning the dial or pressing either the up or down arrow button on the key pad to view the runtime durations of each zone/station. If you are unsure of how to perform this operation, consult your irrigation contractor. If you move on to some of the other outdoor audits in this guidebook, you will be able to make some decisions as to whether these runtimes are appropriate.

If possible, locate your facility’s irrigation system blueprint. However, unless the building is new, the original zone map may not be accurate. It is very common for zones to be added or removed as part of system repairs or other modifications. Therefore, a good first step is to confirm the accuracy of the facility’s irrigation system blueprint or to sketch a zone map. This is done by manually engaging each zone one at a time and indicating the location of the zone on either the original blueprint or on a sketch of your own. The easiest way to do this is to have someone out in the field covering the parts of the property you cannot see from the irrigation controller. By using two-way radios or cell phones, you can collaborate to create a map similar to Figure 11.

Florida Focus

Your local municipality or water management district may issue irrigation variances under certain conditions. These variances usually do not grant more time for irrigation, but allow the irrigation to occur at times other than those prescribed for the area. Consult with your local governing agency directly if you think a variance could benefit your facility.

Figure 11. A sketched irrigation zone map. This

example shows a system with two separate controllers labeled System 1 and System 2.

Audit Objectives

In this procedure, you will locate the irrigation controller or timer and ensure it is set to run in compliance with local watering rules. The procedure will guide you through the steps to:

 Gain or increase familiarity with your facility’s irrigation controller location  Document the irrigation runtimes for each

zone (or station)

 Confirm the accuracy of the original irrigation system blueprint (if zones are indicated) or create a sketch of the facility’s irrigation system zones  Confirm the system is set to run in

compliance with local watering restrictions

67B72B

Audit Steps

1. Fill out the parts of the Basic Facility Header Sheet (page 28) that you think will apply to this audit procedure and any others you want to conduct.

2. Examine Worksheet 12: Irrigation Schedule and Controller – Basic Audit.