Plumbing Supply Piping Planning Tool Reducing Water Wasted Waiting for Hot

Transcription

1 Plumbing Supply Piping Planning Tool Reducing Water Wasted Waiting for Hot Craig Selover Selover Consulting H: C:

2 Floor Plan

3 Floor Plan All Piping

4 WaterSense,HERS, Builders Program Approach Builders actively market their HERS (home energy rating system) rating for Home Energy Efficiency. The focus of HERS presently is Building Science oriented efficient HVAC systems, proper ventilation for Indoor Air Quality, Efficient Water Heating, proper heat, air and moisture control Plumbing System components which dispense Hot Water at lower flow rates can further improve energy efficiency through hot water demand reduction. Modifications to HERS programming to include this component are in process.

5 Indoor Water Indoor Water Lavatory Faucets 1.5 gpm Showerheads 2.0 gpm HET Water Closets 1.28 gpm Engineered Plumbing Design and Insulated Hot Water Piping minimize water wasted waiting for hot (water, energy savings and homeowner convenience) Include ENERGY STAR dishwashers Discuss ENERGY STAR Clothes Washers as an option Apply WaterSense specs for evaporative coolers, water softeners and water filtration/purification devices

6 Plumbing Water Supply Design Builder house plan designs rarely contain a design layout for the water supply system Plans contain Water Heater and each Fixture location, only Plumbing Contractor determines how the piping gets from the water heater to each fixture. Plumbing Codes control pipe sizing to ensure sufficient pressure to each outlet to allow for adequate flow rates to supply the demand of shower valves, faucets, water closets and appliances.

7 Plumbing Codes WaterSense flow rate specifications for showerheads and lavatory faucets lower necessary pipe sizes. Current research may result in allowing some reduction in the required pipe sizes This could result in beneficial reduction of the time it takes hot water to be delivered to faucets and showerheads

8 Plumbing Plan Design A simple spreadsheet approach to comparing piping layouts and volume in hot water piping to reduce water wasted waiting for hot Spreadsheet output provides an estimation of: Time to get hot water at each hot water outlet Volume of water wasted waiting to get hot Included in the calculations are a standardized set of hot water draws at each faucet and shower that start with the water in the pipe being cold The cold start number of draws is based upon basic field research in homes, and provide 2 person and 4 person scenarios

9 Cold Start Scenarios Number of Hot Water Draws Starting from Cold MBR Lav Kitchen MBR Lav 1 2 MBR Shower Bath 2 Lav 1 Bath 2 Lav 2 Bath 2 Shower Bath 3 Lav Bath 3 Shower Bar Powder Lav Family of Family of Estimates of the number of cold start draws of hot water for 2 or 4 occupant homes. As a standardized number of cold starts, this allows for comparison of various piping configurations and recirculation types. Note that weekend cold starts tend to be higher than weekdays. As Plumbing Codes change to require hot water pipe insulation, we will need to estimate what the reduced number of cold starts might be as the insulation keeps the water in the pipe warmer between sequential uses. More data needed to characterize this.

10 Plumbing Plan Design A simple process, starting with the floor plan: Water heater location Each shower and kitchen or lavatory sink location The planner applies Code pipe sizing rules: Starting at the water heater Uses the dimensioned floor plan Enters the number of feet of each size pipe in basic orthagonal directions (North, South, East, West, Up Down)

11 Example Home Example: Simple Arizona Slab-on-grade Ranch home. 3 Bedroom 2 bath with Kitchen Master Bath Shower, double bowl sinks, Whirlpool Tub

12 Basic Up-Down Dimensions

13 Floor Plan - Water Heater to Kitchen Step 1 The longest pipe run in the home will be to the kitchen sink. Next Steps are to lay in the piping network, marking the points where piping branches off, and begin filling in the Pipe Layout Tab on the Spreadsheet to log in the various pipe diameters, lengths and directions. In running through this example, you can refer to the full size drawing to estimate the distances. Add the water heater outlet riser, ¾ Up (4.25 feet) to attic (beneath insulation), note 9 Ceiling height. Add a ¾ inch pipe trunk run East (31.5 feet) to the point where the kitchen pipe turns North. The entries to the spreadsheet are shown below.

14 Spreadsheet Water Heater to Kitchen Pipe Length/Size Direction 1" 3/4" 1/2" 3/8" Cups Gallons On a Recir c Loop Real Gallons Kitchen Faucet WH to attic UP x mbath shwr East x to b2 shwr North x b2 sink Down x 0.00 North x 0.00 twig twig Supply Total

15 Step 3 Master Bathroom Sinks, add a branch extension from Tee at Kitchen Bend to the East (6 feet, now ½ inch), then South (2 ¼ feet), then drop (8.25 feet), and run a twig of flexible supply (2 feet ) to each lavatory sink faucet. For the each sink, add in the feet of ¾ inch pipe from the water heater to the kitchen bend. For the second sink in the Master Bath, copy in the length of ½ pipe summed up for the first sink. Master Bath From Kitchen Tee East x 0.00 South Down Lavatory 1 twig Supply Total Lavatory 2 twig Supply Total Master Bath Portion

16 Master Shower Step 4 Master Bath Shower. Add ¾ branch line from Tee off main line to kitchen (1 foot short of bend to kitchen), South (9.75 feet), then a ½ inch pipe drop (5.25 feet) from above ceiling to 4 foot above floor to valve, and a ½ twig as the riser from the valve to showerhead (4 feet). Also, you must include the water heater to tee distance of ¾ pipe from the kitchen run (34.75 feet) Total kitchen-1 foot South Down twig Shower/Tub- Shower Combo twig Up Total

17 Master Tub Step 5 Master Bath Roman Tub. Add in ¾ piping total from water heater to shower drop (44.5 feet). Add ¾ pipe East (9.1 feet) to above wall with tub faucet. Add ¾ drop (8.5 feet) to stub-out for Roman Tub Valve. Add ½ inch twig (2 feet) or flexible supply to valve. From Shower South Down twig Up Roman Tub twig

18 Bath 2 Shower Step 6 Bath 2 Shower. The Bath 2 Shower drop branch is 6.75 feet short of the kitchen bend. Add in ¾ pipe to the spreadsheet as feet less 6.75, or 29 feet. Next is the drop of ½ pipe 7 feet down from above the ceiling to the shower valve (2 feet above finished floor). Finally, a ½ inch ( 5 foot) riser to the showerhead is added.

19 Bath 2 Lavatory Step 7 Bath 2 Lavatory Piping. The Bath 2 Lavatory ½ inch piping drop will be 14.5 feet short of the kitchen bend. Enter feet less 14.5 feet (21.25 feet) of ¾ pipe into the spreadsheet. Then add a ½ drop (8.25 feet) to the lavatory stop stub-out, and a 2 foot 3/8 flexible supply twig. Kitchen Tee x Supply Lavatory 1 twig

20 Summary Calculations Cold Start Events Cold Start Events 4People With Recirculation Pipe Volume Actual Water Gallons Volume Flow Rate Time Water Wasted Wasted Location Fixture Fitting or Appliance Cups (16 # of cups/gal) F=1.25 (gpm) (seconds) Events Gallons Heat Loss Wait Time Gallons Heat Loss Kitchen Faucet Master Bath Lavatory Lavatory Roman Tub Shower Bath 2 Lavatory Lavatory Roman Tub Shower Bath 3 Lavatory Tub Shower Combo Bar Faucet Powder Room Faucet BTU / day Total Gallons Wasted per day BTU / day Gallons per year BTU / yr BTU / yr Therms 0.48Therms

21 Summary Simple tool Allows comparison of: Standard trunk, branch, twig piping designs Local (sub) manifold or home run manifold design Options for demand controlled recirculation Provides: Estimate of energy wasted on water wasted waiting for hot water Delivery times with respect to homeowner convenience What interest is there from Water Utilities in participating with pilot homes experiments to learn about potential savings?