Hot Water delivery

Water saving hot water delivery is becoming increasingly important.

In the following article, Tom Rendall from Australian Water & Energy looks at the problem in detail and provides answers to many relevant issues.

In today's modern home construction the Australian Plumbing Industry in general faces an almost impossible uphill challenge to deliver hot water efficiently and effectively, as well as sustainably to all points of the home. It is not the HWS or its Star Rating that is responsible for the amount of water loss, it is the plumbing design and distance from the HWS to the point of use. In the 1970's the standard home had on average between 5 and 9 hot water outlets plumbed compactly and directly.

In today's new homes the number of hot water outlets is between 9 to 16 plus given the design/floor plan and number of bathrooms etc. In trying to deliver hot water efficiently the Plumbing Industry also has confines and restraints placed on it by Government Sustainability Building requirements and the floor plan or overall size of the new homes being constructed. So can we rectify the problem of poor hot water delivery and successfully overcome it even when governed by these physical restraints? Yes we can.

But, firstly we need to understand some of the construction parameters that are influencing and extenuating this problem, with the introduction of the Concrete Slab construction the inability to plumb direct underfloor has made it necessary to plumb around or over the structure. For cold water no big deal, but it increases the pipe run for hot water, in doing so it increases the water and heat (energy) losses. Secondly, low flow fixtures, not an issue for cold water, but by slowing down the flow of hot water during the delivery phase combined with the additional length of pipe metres required to deliver hot water, we have a serious water and energy loss issues. International research conducted between 2003 & 2005 shows that the slower the water flow the more heat loss. For every volume of water that has cooled in the hot water pipe you lose an additional 2 volumes to heat loss during delivery, 3 pipe volume in total. It is also a misconception to believe that Polyethylene type piping most commonly used in new home construction is self insulating, wrong, it radiates heat to the atmosphere just like un-lagged Copper Piping. As a conductor of Electricity it is self insulating, but not heat loss from the water contained in it, always Insulate or Lag hot water pipes.

There are three distinct phases to a hot water event (a) delivery (b) use (c) cool down. Upon opening a fixture, hot water leaves the HWS via the hot water piping toward the fixture. The delivery time should be as short as possible. A hot water delivery phase in all probability has two distinct parts to it.

The first part of delivery is structural and depends on:
• Plumbing system configuration.
• Location of the pipes.
• Volume of the water in the pipes between the HWS and the fixture.
• Whether the piping is insulated.
• Fixture flow rate.
• Temperature of the water in the pipes compared to the temperature in the water heater, etc.

The second part is user behaviour and depends on when the user decides the water is hot enough to use.
Usage phase or the length of time it takes to perform the task for which hot water is required.
The cool down phase begins immediately the fixture is turned off. Depending on the duration between the next hot water event if short enough, the water in the pipe all the way back to the water heater will still be hot enough to use.
If the duration between events is too long, the water will have cooled off and water will then be run down the drain again until the correct temperature hot water arrives at the fixture.

At point of use hot water is generally mixed with cold water at the fixture to reach the desired usable water temperature.
Therefore the thermostat control on the HWS or Tempering Valve needs to be set to the maximum allowable temperature under the plumbing code to assist in overcome the heat losses through the piping, but still provide water that is hot enough to be mixed at the farthest fixture providing the user with the desired useful hot water temperature.

So what is the solution to this problem?

For the past 10 years in Australia the technology and plumbing knowledge has been available to rectify inefficient hot water delivery in new home construction. Why then is it still not required in the Environmentally Star rated homes that are currently constructed in all States? Because until now the Governments and Building Industry have not been interested in addressing this issue, they are leaving the solution up to you the plumber to fix, you are their environmental scapegoat. The solution is simple by using modern technology and a smart hot water plumbing design (Structured Plumbing) you can deliver hot water to any fixture regardless of floor plan and waste no more than 1 to 2 cups of water waiting for hot water to arrive. In the process using far less energy than flushing the water down the drain.

For approximately every 20 litres of water wasted waiting for hot water to arrive 1 kWh of associated energies are lost.
The average home wastes around 15,000 litres of water per annum waiting for hot water.
That's around 750 kWh of associated energy lost per house hold and being paid for by the home owner.

So how do you achieve sustainable hot water delivery and waste no more than a cup or two of water during the delivery phase, firstly, the hot water supply is required to be within 1 or 2 cup volume (or Dropper/Riser Pipe volume) from the hot water supply.

(1 cup volume is 2.3 metres of 15 mm Polyethylene type piping.)

As homes are currently plumbing for hot water this is not really practical or possible as it would required to have a HWS at all hot water points to achieve this result. Or would it?

Consider this, what if we make the main Hot Water supply pipe the direct source of hot water. All you would then require is to have all the hot water fixtures installed within 1 to 2 cups Pipe Length volume from the hot water supply or 2 to 4 metres 15 mm pipe. By using the correct and proven on demand hot water recirculation technology such as an ACT D'MAND® Kontrol® System located after the last fixture (or a similar Water Marked approved product if available).

By priming the hot water pipe on demand prior to turning on the hot water fixture, you bring the hot water to within 1 to 2 cups volume of the fixture. So if the home is plumbed using the correct Structured Plumbing principals, this effectively eliminates the need of multiple hot water heaters and reduces both water and energy wastage to a minimum. Water that would normally be wasted is returned to the hot water heater and as the water is being delivered more efficiently it provides a min 20% energy saving in the heating of the hot water. These savings have been well documented in International research conducted using ACT D'MAND® Kontrol® System technology and proven locally through installations of the system and technology Australia wide.

So how do you correctly Structure the hot water plumbing in new home construction?

These few points will provide you with some guidelines to follow.

New home construction, an on demand operated flow and return loop or Ring Main should be used to reduce water and energy loss.

Both Cold and Hot Pipes must be of equal size 3/4" or 20 mm (diameter) min.
All Hot water pipes must be Insulated with the correct R rating as per Plumbing Code.
All dropper or riser pipes should be plumbed in 1/2" or 15 mm and should be kept to a minimum length between 2 and 4 metres and Insulated for at least the first metre.
Limit restrictions to flow rate, Pipe direction change should be done by using a wide sweeping radius curve and not a 90° Hard Elbow (Hard Elbow effect the flow rate and inhibit efficient hot water delivery.) 1 x 90° Hard Elbow is = to 1.5 metres of Pipe in resistance to flow rate.

The ideal location for the on demand recirculation unit is within the first few metres of the return pipe after the last fixture, this eliminates the need to insulate the return pipe to the HWS. (The most water and energy efficient location in terms of operating time and water drawn from HWS.)

If the on demand recirculation system is located at the HWS then the whole of the return pipe must be insulated and a weather proof cover used to protect the Pump and electronics'.

Important Note: New home construction, the main supply water pressure is restricted at the water meter to 500 kPa, if this is so then the 500 kPa PLV that is supplied with all new Solar HWS is not required and should not be installed. This will only create additional flow rate issues and pressure drop in the hot water supply. (Always check the Mains pressure first.)

If on demand hot water recirculation is installed with an Instantaneous type HWS a Duo Valve should be used in place of a Gate/Ball Valve on the cold water feed to prevent the possibility of backflow, or a Non-return Valve used in conjunction with the existing Gate/Ball Valve.

The connection of the return pipe to the HWS will be at the cold water inlet to the HWS after the Duo Valve.
Added note, the cold water connection for the Tempering Valve must also come off the same pipe after the Duo Valve.

Installation of system must be carried out in accordance to the Australian Plumbing code AS3500 and the product manufactures Installation Instructions.

ACT D'MAND® Kontrol® System technology can also be very simply retro fitted to existing homes without any special plumbing required at the furthest fixture. Effectively assisting to overcome water and energy wastage issues in hot water delivery in existing homes.
Retro Fit by using the cold water pipe as a return to the hot water heater and will work with all mains pressure hot water heaters.

(Pressures in hot and cold pipes must be equal.)

But beware as there are a number of products available that claim to save water and energy.
Some operate by diverting the water into a storage tank requiring additional plumbing and a tank etc.. Others operate on a timer and temperature switch control system, these units do not save Energy and can be in some cases costly and complicated to install.

Extensive research has shown that only a true on demand ACT D'MAND® Kontrol® System hot water recirculation system can offer the homeowner true water and energy savings. When researching plumbing products of this type it is always advisable to look at what the manufacturer has to offer in terms of product quality and longevity.

Of all the hot water saving products available the ACT D'MAND® Kontrol® System stands out, it's the original that was developed over 20 years ago. The one that other manufacturer have tried to copy or mimic without much environmental success. In new home construction or existing dwellings sustainable hot water efficiency and delivery is genuinely possible at the press of a button. You can turn an existing HWS into an water and energy saving instant hot water supply system that the home owner is in control of. The ACT D'MAND® Kontrol® System can be activated by (a) Hardwired Button (b) Wireless Remote Control Kit (c) Hardwired Motion Sensor a Wireless Motion Sensor option is also available. (All activation controls are low Voltage.)

Just 3 simple steps to getting hot water.

Press button.

Wait for the hot water to be drawn forward (you do this now but watch your water and money going down the drain) ACT D'MAND® Kontrol® System turns off on the approach of hot water.

Turn on the fixture and within 1 to 2 seconds hot water arrives.

The solution to correct hot water delivery is here, it is a simple and effective way to solve the problem you face every day of how do you plumb hot water deliver efficiently and environmentally. Add an ACT D'MAND® Kontrol® System to your tool kit to fix hot water delivery issues.

For information regarding the ACT D'MAND® Kontrol® System and Structured Plumbing Design go to:

www.auswaterenergy.com.au

(*Hiller, Dr. Carl, P.E., 2005. Hot Water Distribution System Research – Phase 1, California Energy Commission, Sacramento, California, November 2005, CEC 500- 2005-161. The full report can be found at: http://www.energy.ca .gov/pier/final_project_reports/CEC-500-2005-161.html)
*G Klein: Structured Plumbing Offers Real Benefits 2008, Issue 1 World Plumbing Review.

Author: Tom Rendall, Australian Water & Energy Pty. Ltd. April: 2013

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ISSUE 3 - april/may 2013