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What Are the Components of a Greywater System?

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Most homeowners are concerned about energy savings, but water savings will be the big deal on the horizon. You may hear about greywater, and how you can use it in your home, but can you buy equipment like you would for energy savings?

I have the habit of browsing when I am in a hardware store or home improvement center. I like knowing what products are available; how much they cost; and is there something new. I want to be prepared when speaking with clients. Typically I meander without intent; however, I was at a store this past Earth Day, where I was handed a brochure fo Earth Day specials at the door. The brochure promised savings on items that are part of the Earth Day spirit. That was hardly so, but this put me on a mission. Sure, you can find many products that will help your home becoming greener at these stores, but can you find products that will save you water? As water prices rise, homeowners may want greywater systems, or consider how to use water in a smarter fashion.
    You may be aware that Houston and other area will be increasing the amount you pay on your water bill. As higher energy prices drove consumers to energy efficient appliances, higher water prices will see the increased interest in reusing water in the home. The water that we can reuse is called greywater. Potable water is the water coming into your home. This is the water that you can drink, and you should have backflow prevention (anti-siphon) devices in your home to ensure that this water remains clean. After the water has been used, we refer to it as either being greywater or blackwater. Blackwater is water that cannot be reused, so this would be water from the toilet. Greywater is the water from washing dishes or your hands. This can be used for other purposes around the home, which do not involve consumption. I know that there are greywater kits available through internet sites, but I was wondering about finding these products at local stores. I discovered that we are not there yet, so I thought I would share some features of what a greywater system could include if you wished to install one on your own home.

Using Greywater for Your Toilet

    You do not need clean drinking water to flush your toilet. This is a perfect greywater application. You could take water from a tub, shower,or sink to refill the tank on your toilet. Shower drains are harder to access on most homes, so we may loose precious water for our imagined system. Tubs frequently do (and they really should have) an access panel on the wall behind the tub valves. Sinks (lavatories) in the bathrooms are easy enough to access, but if you have a pedestal sink, your greywater system may need some thought to make it look better. You can find low flow shower heads, low flow toilets, and low flow aerators for faucets, but you will have to be creative with products at your hardware store to make all of this system. When the water drains, it goes into a tailpipe which leads to the p-trap. The p-trap looks a little like the letter p on its side. The purpose of the p-trap is to prevent sewer gas from coming into your home. If we take the water from the tail pipe or after the p-trap does not matter, but we need to remember two things: 1) we want to stop the sewer gas from entering our home; and 2) we may want a catch feature for items that drop into the sink to prevent them from going further (something a p-trap does). Taking the greywater from after the p-trap makes sense to me. To stop the sewer gas, I would cap that pipe. If the pipe is pvc, we could glue on pvc cap. This is standard items to find at the store. PVC is perfect for our diy project, since it is easier for a homeowner to handle. We now need to get this greywater to the toilet tank. This is uphill, so we cannot use gravity to help us when using water from the same bathroom. Water in your plumbing system uses pressure to force it to the different parts of the structure. To use this pressure, we would have to add this potable water under pressure to our greywater to put it under pressure to move it to the tank. The other option would be a pump that forces the water to the toilet tank. In either case, I think we should consider an additional tank to hold the greywater before it goes to the toilet. The amount of water from the tub could be a quite large in volume.
    The storage tank could be a rain barrel or other water storage device, so we can find something at the store. The real problem becomes were do we place this storage tank. Outside of the home makes sense for this amount of water, but you have to see what is practical for your own structure. For example smaller tanks could be in a bathroom cabinet or over the toilet itself. Another location could be in the attic. Once we have this tank, we need to consider how will the water flow into it, and how do we get the water out. Depending on the location, we can use gravity, pressure, or pumps. For example, if the storage tank is in the attic, we can use a pump to force the water up to the storage tank, then gravity could feed the greywater to the toilet tank. Using the water pressure in you potable water plumbing system brings another concern. Let us take the water from our cold water supply line, and feed it into our greywater tank. There should be a backflow prevention device in this cold water supply line, and the storage tank should be able to handle this pressure. A water heater tank can handle the pressure (we do not need to light it), and there are backflow valves available in the stores. A simple backflow valve is the one that you can buy for your exterior hose bib. Hot water tanks also have a drain valve that would let us use gravity. Maybe we can find an use tank that can still hold water? Another storage tank option are the tanks for pool equipment. Pool equipment may also offer us the pump we need, but there are smaller pumps, such as for fountains.
   Once we have dealt with the greywater storage and delivery, we have to deal with feeding the water to the toilet tank. Your standard 3/4″ pipe for water delivery in your home works with most of our tank storage choices, and this can attach to your feed line for your toilet tank. This feed can be pvc pipes too. The problem that you may face is having the pipes exposed to view. Pex tubing can be fed through the walls much like wiring, so this can be a good option for diy homeowners. You will need the valve to turn off the water to the toilet, so you can work on it. The valve that is there should be left in place to keep the potable water supply turned off. This means that you need your own greywater shutoff. Again, this is a standard valve at a store.

Watering Plants with Greywater

   You may have heard of using greywater to water your plants, so let us consider an option. In my scenario, we are using the greywater from tub, shower, and bathroom sinks for flushing our toilets. We do have other greywater options. Other sinks in the house, dishwasher, clothes washer, and primary drain line for your air conditioning system are all options. Most of these appliances sit on an exterior wall, so we could create a new drain going out the wall at those points. I have seen people run the lines out of a window, but this has problems. We will face the same issue with p-traps as we did above. We also will want to prevent water from back flowing into our appliances, so having the pipe go above the normal drain, then down creates a highloop, which will stop water from coming back into the home. As the pipe leaves the wall, we will need to seal the opening to prevent moisture and pest problems, and for energy efficiency. If you wish to use this water for a sprinkler system, we face the problem of delivery again, so storage tank and pump would be needed. Why not forgo the sprinkler with a drip irrigation system? Have the waste water flow into a system of pipes delivering greywater to your garden beds. This takes away the need for a good deal more equipment, and we water when we wash. We may over water with this method, so I would consider moving the drip irrigation to different beds, or having a manifold to turn on water to one bed, while shutting it off for another. (A manifold is a series of valves on one pipe which directs water to different supply pipes).
    Are you still with me? Long post, but I wanted to give you the idea of what could be possible for a greywater system. Soon enough we will see specialty equipment available in our local stores. I can remember four years ago there was a discussion of rain barrels as a great thing to do for your home. I only recently noticed that you can now buy small rain barrels in the stores (and I made my own from old trash cans). Once a dedicated group touts the advantages of some method, we see manufacturers making those products easier to buy; however, why not be ahead of the curve.

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3 Responses to “What Are the Components of a Greywater System?”

  1. thanks!

  2. Andrew Says:

    Cool post – thanks for sharing this. Based on extensive experimentation, I want to recommend my favorite option for where to send greywater: to edible plants via the soil. Even if you don’t already have a garden that requires irrigation, you can plant fruit trees at the time of installing your system. Two major advantages of sending the water into the soil near fruit trees are that you’re eliminating the use of potable water for a purpose that doesn’t require it and, by going straight to the soil you don’t need to store greywater. Note – you’ll need to use greywater friendly cleaning products and you don’t want to deliver greywater to root veggies or edibles that would come into direct contact with your wash water.

    At http://www.cleanwatercomponents.com there is a load of information on how to install a system safely and correctly. They provide information on how to install a laundry or a shower system, address pathogen concerns with edible plants, and also sell all the parts you’ll need to install your own, super low maintenance, DIY system at your home.

    Its a great thing to be watering your trees while you wash your laundry or take a shower! Check it out!

  3. Hello Andrew,
    your site looks like a good resource for those who wish to delve into this topic more.

© Frank Schulte-Ladbeck Professional Home Inspector Houston, Texas
Frank Theodor Schulte-Ladbeck
home inspector, TREC# 9073
Houston , Texas , 77063 United States

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