Saving Water With a Central Manifold System

There are a few everyday scenarios that pierce the heart of every homeowner – perhaps most pointedly women and mothers. One is the wait for the hot water to arrive at the tap, as we watch gallons of fresh, perfectly drinkable water go down the drain.

Waste. Even non-environmentalists are offended by senseless waste. Wasting water is particularly offensive because we know we need it to live and we probably also know that many people throughout the world don’t have enough. Raise your hands, moms–how many of you have not thought about your children and what their future holds for them as you wait for hot water to arrive at the tap?

There are lots of ways, in all ranges of cost and practicality that minimize water waste in a home. The one I want to discuss today is a Central Manifold Plumbing Distribution System.

This is a wonderfully simple concept that can save lot of water and has some other benefits as well.

What Is A Central Manifold System?
Most residential plumbing systems consist of a hot water tank heater that feeds a central hot water pipe that serves the whole house. Smaller pipes branch off of this central line (like secondary roads off a beltway) and go directly to each faucet in the house. The problem with this type of system is that the hot water in that central pipe doesn’t stay hot for very long, particularly in the winter. So when we go to take a shower first thing in the morning we have to drain all of that water out of the way to get to the hot water from the hot water tank. Unless you have some sort of nifty recirculation system, you waste a lot of water because of this every day.

A Central Manifold System is different in that there is no central pipe. Instead, there is a manifold box that is installed on a wall near the hot water heater that acts as a little junction between the heater and the water fixtures in your home. The water from the water heater goes directly into the manifold, which has multiple sections of small PEX tubing running off of it to each individual fixture in your home. Because the tubes are flexible, there are no pipe-fittings (T’s or elbows) that could spring leaks behind walls, floors or ceilings.

Why It Saves Water
This is really simple. If you eliminate the central line in a system, you eliminate a large diameter pipe that holds dozens of gallons of hot water that inevitably grows cold and is wasted.

A manifold system provides a one-way trip from the hot water heater/manifold system directly to the fixture. It is a teeny-tiny piece of tube, so all that you waste is what is in that one tube between the manifold and the fixture. Think of an octopus – the head being the water heater/manifold and the arms being the tubing that runs directly to each fixture in your home. (You could substitute a spider in for this analogy, but I hate spiders and I bet you do too.)

Other Benefits Everyone has experienced leaks in their homes and most of us would like to minimize those risks. A manifold system does this because there are no hidden fittings or connections except at the fixture and the manifold itself. Even if you develop a hot water leak, you know it can only be coming from one of a couple of places.

Hot water also arrives to the tap faster. So you waste less time and less water.

Servicing is simplified too. Let’s say you have some sort of plumbing issue in your kitchen. The plumber doesn’t have to disengage all water service to your home while he works on that one fixture. He simply closes off that one individual ball valve inside the manifold. Your kids can still shower; you can clean the bathroom, etc.

A Tale of Two Plumbing Systems
We own two homes, our former residence, which is now a rental, and our current residence, the Greenspiration Home.

I well remember the frustration of waiting for hot water to arrive at the tap in our old house. It was a standard central line system and the master bedroom bathroom was the farthest fixture from the hot water tank. I knew we wasted a lot of water but I didn’t really have anything to compare it to until now. So I asked our renters, a young couple with two small children, to measure how many cups of water flow from the master bedroom sink fixture (after several hours of disuse) until the water gets warm to the touch. I did the same in the Greenspiration Home where we have the central manifold system. The results were shocking.

It takes 2 cups of water flowing before the water in the Greenspiration Home gets warm. It takes 30 cups of water flowing before the water in our renters’ home gets warm! Granted, our current master bathroom is closer to the hot water heater than in our previous residence, but still, the amount of water being wasted in our rental home is staggering. It makes me feel a little sick, actually.

I have found that builders and contractors who aren’t familiar with central manifold systems are leery, but don’t let that stop you from considering one for your new home. In some regions of the country, this is the primary type of distribution system that is used. Where this isn’t the case, contractors (and builders) may need some convincing. (Not long ago, a builder tried to argue with me that central manifold systems don’t save water; so never ever underestimate how desperately contractors will cling to what they know and eschew what they don’t. Just remember – it’s your house, it’s your water, and it’s your decision.

4 Responses »

  1. Hi,

    thank you for this article,

    would it be possible with central manifold to connect one of them to rain water or sump pump? for instance, it would be beneficial to use drain water for the toilet flushes or the garden hose.
    It would require a system that taps on the water line when the drain water reservoir is empty, and maybe it would need to filter the drain water to avoid odors or plugging.
    Are such systems available? one can guess it could save a lot too.

    Thank you for your input on this,


    • Hi David,

      Thank you for writing. I haven’t heard of such a thing, so you would need to check with an experienced plumber (and probably a code official) to find the answer. I assume you are talking about a system that is completely separate from your fresh water supply. In my case, the manifold is only routing water from my water heater and my fresh, clean cold water supply.

    • Yes David. Its grey water plumbing. I can’t tell you about the central manifold system, but yes you need to check with the codes, and if they don’t approve of it, try to change the policy through outreach.

      Here in Seattle, the county has approved of grey water use and other counties will do so soon because of our outreach for years. That said, you can plumb now if new house (harder in retrofit) unless your gutting out, and hook up after the codes are updated. It will be much much cheaper.

      Some toilets now have faucests built into the tops tank, that fauset is hooked up from cistern or plumbed in grey water unit, or gorilla’d in by homeowner.


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