Explaining the concept of a Hot Water Plumbing Loop

Posted by Benjamin Close on February 21, 2009 under Country Living | 8 Comments to Read

Example Of A Houses Plumbing with / without a hot water loop

Example Of A Houses Plumbing with / without a hot water loop

One thing that a lot of people don’t fully understand is the concept of a hot water plumbing loop (also known as a hot water return or a ring main). The reason for this is not really all that surprizing. Anyone with mains water to their house probably wouldn’t even care about the concept. Most builders won’t offer it as an option, most plumbers aren’t aware of it but the benefits of it are huge. Especially in Australia with drought conditions and water restrictions, even on mains water a hot water plumbing loop makes a lot of sense.

What is it?

Put simply, a hot water plumbing loop means that the hot water pipe from one tap to the next continues around in a loop back to some location (normally the cold water inlet to the hot water system). The picture helps to explain the concept.

In a normal plumbing setup there is normally one main hot water line. This line breaks up into branches. These branches then can further split but end up eventually at the various hot water taps.

In a hot water plumbing loop, also know as a closed loop or a sometimes a gravity loop, the line from the hot water system continues from one tap, to the next. There is no branches as the line continues until it loops back to the hot water system.

How does it work?

Now that you know what it is, your probably wondering why anyone would want it. It all comes down to water conservation. I’m sure at some point you’ve turned on your shower, felt that freezing water coming out and had to wait for it to get hot. Or you’ve run the kitchen tap until the water became hot. The hot water loop eliminates this water wastage. Instead of the cold water going down the drain, it is instead recycled back to the cold inlet of the hot water tank. The water is then reheated and reused.

There’s a number of different ways a hot water loop can be implemented. You can use a pump with a press button near each tap to start the hot water cycling in the loop. You can also setup a gravity fed system which continually recycles. Or you can use a continual pump to recycle the water. This way as soon as you turn the tap on the water is hot!

In a gravity fed system hot water is cycled from the top of the hot water tank, back down to the bottom of the hot water tank. A gravity fed system requires a lot more planning as it requires that no hot water pipe ever goes higher than the hot water system.

What type of saving is achievable?

The cost for installing a gravity feed type system is around $300 – $500 different depending on the house, how many taps it has, the distance to the hot water system, the pump used and whether it’s automatic or manually controlled (ie manual push button to start the cycle).  This is the main reason builders don’t offer it – it’s not competitive for the builders to do so. It’s also not cost effective for the average home owner due to reasons mentioned below.

The savings in water you get can be quite staggering. Take a typical shower with a water saving shower head. These typically use in the range of 9 litres of water per minute. Now if it takes 2 minutes before the water is hot enough to shower that’s 18 litres that’s normally going down the drain. Now multiply it out by a year:   18 * 365 =  6570 litres go straight down the drain! If you have 2 bathrooms this doubles! Then there’s the kitchen, laundry, etc.. it adds up very quickly.

It’s also the reason that people who have mains pressure water to their house often don’t care. What’s 6570 litres of water over a year? Just pay the water bill ( about $5 AUD at a rate of 71cents/Kl) and be done with it. However, when you don’t have mains pressure water that makes a big difference.  Our place at Gould Creek is one such example. Our total tank storage capacity is 2×23500 tanks. Hence 6570 is almost 14% of our entire storage capacity!

With drought in Australia beginning to affect South Australia and Victoria very heavily, the attitude that it’s just water, I’ll buy more needs to change. A hot water plumbing loop shifts perception back to what it should be – less about money and more about saving our precious environment!



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  • avatar

    Bricks, Roof, Plumbing, Electrics, Insulation and now Gyprock! » ClearChain said,

    […] plumber on the other hand really had no idea. We requested a hot water plumbing loop but this was not done.. well not properly. 1 call to the super and he said he would take care of […]

  • avatar

    kush said,

    want to no more on plumbing,hot and hot connetion with the picture attach thanks

  • avatar

    Woz said,

    Thanks, this has been very helpful. plumber installed new instant gas HWS and seems to have done a ‘half loop'(from what I gather, no better than branch) instead of the orginal branch. Also taking the longeset possible route (first tap in series is the furthest from the HWS then back again, causing very long delays in hot water reaching the taps). The diagram is the best explaination I have found, enough for me to question the installation and call in for 2nd opinion.

  • avatar

    William Gustavson said,

    Where can the parts be purchased for installing this loop system?

  • avatar

    Larry said,

    I installed a loop with a mechanical pump and have also added a timer and a heat sensor on the return side to shut down the pump when not needed all works well except I get a small amount of hot water from the cold fauset and it was suggested that I add a small pressure tank to the system and that should clear it up. I don’t understand the principle of this or where the tank should be installed on the hot water leg or the cold water leg. I have also changed the hot water return from the cold side to to hot side and this made it much worse.I will change it back again. All help will be much welcomed

  • avatar

    Benjamin Close said,

    Whilst I’m no plumber my guess is to deal with a pressure drop in the cold water line. Imagine a tap in your house

    C —- Faucet — H

    Now if there is a drop in pressure on the cold line hot water will flow through the T junction leading to the Faucet back into the cold line. This may happen each time the pump kicks or when you use hot water (since some cold flows back into the HW tank). Hence you get hot water on the cold line. A small pressure tank on the cold line should fix this as there will be no drop in pressure on the cold side so no back flow through the faucet to the cold line

  • avatar

    terry p said,

    I was told that if the tank is in the basement, and all fix are on the main floor,above the tank that gravity will work,as the hot water wil rise and the ccol end will fall back down to the tank?

  • avatar

    Sara Gentile said,

    Indeed, this new technology affects very well and contributes a big impact towards mother nature, especially, now that drought is looming. Thankfully, this new technology is studied well by reliable plumbers, who takes part not just on installation or on emergency hot water services, but on sharing information and helpful tips about this as well.

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