...and distributing it round the garden

Factors such as the type of garden, gradients, soil type, and the volume of greywater and its flow rate will determine the best method for distributing the greywater to your plants. The main options are mulch-filled trenches, or some sort of dripper hose (or ordinary hose with holes poked in it) either subsurface or under a layer of mulch.

Golden rule for distributing greywater...
Use sub-surface distribution, and ensure the greywater does not come in contact with food that is eaten raw. For example, sub-surface use of greywater under fruit trees is fine, as long as you don't eat any fruit that drops to the ground, but splashing it over your lettuces is not! (Also keep greywater away from children and pets.)

However, note that published guidelines relating to the use of greywater for growing food vary (and some people use greywater to grow everything they eat). Health departments in some states say what I said above, some say don't use it to grow anything at all that you eat, and the Victorian health department gives conflicting advice depending on which of their publications you read! Similarly, most health departments seem unconcerned about where or how you tip a bucket of greywater on your garden, but if it is a larger quantity they say you must deliver it sub-surface. All washing machine water potentially carries some E. Coli but never-the-less is considered safe, whereas its not considered safe to reuse the laundry water from washing nappies. Its all based on relative risk levels (whether there is a low or high quantity of pathogens likely to be in the water), and a degree of commonsense does not go astray. What kid did not try drinking the bathwater at least once?

Bear in mind that any pathogens in your shower greywater will have come from members of your household and are probably generally spread around your house already. For example, you'll risk getting Cholera from veges grown with greywater only if someone in your house already has it! The only water available for growing vegetables in my grandfather's garden was the greywater from his bathroom and kitchen drains. This would flow into a big tub near the back door, and he would then bucket it onto his vege patch. This would have contravened 5 or 6 of the current greywater guidelines - and they all lived to tell the tale. No, I'm not encouraging you to do it his way. I'm merely trying to provide a counter-balance to the alarmed reaction - "Oh my goodness! Greywater is dangerous. I wouldn't risk my family's health." - that many people must feel when reading the health department guidelines.

Mulch-filled trenches...
This is the cheapest option and, provided your garden has suitable conditions, is probably the easiest method. Simply dig a trench about 15cm deep and 15cm wide along where you want the water to go, then fill the trench with loose mulch. Poke the greywater hose (the other end of the hose that is attached to the pump outlet) into one end of the trench and hold it in place with a stone, tent peg, or whatever. You'd probably want to have a number of trenches, perhaps one for each day of the week, and to move the greywater hose between them in rotation.

Trenches work well if the ground is fairly level or has a slight downward slope, if the soil is not too permeable, and if the volume and flow of greywater is sufficient for it to reach the end of the trench before all of it soaks into the ground. Each trench needs to be long/deep enough to accomodate all the shower water, but short enough to provide reasonably even watering along its entire length. I suggest starting with a trench about 3m long and experimenting. Tip - before you put in the mulch, do a trial run to check the trench length and also to smooth out any bumps impeding the water flow.

What I've done...
I've successfully used the trench method for delivering laundry greywater to established fruit trees, roses, and perennials (but it can be used for shower water too of course). My trenches are all 3-4 meters long and are filled with pine needles (but any sort of mulch that covers the water and allows a reasonably good flow is fine). The trenches run just to one side of the trunks of the plants (over one side of their root zones). Obviously this does not deliver water to the entire root zone of any of them, but they seem happy enough.

I have one main greywater hose taking the water from the laundry to the front garden. I either poke this hose into the trench that is closest to the house, or connect it to one or other of the extra lengths of hose going to the other trenches. Rubber push-on joiners, like the one I'm holding in the picture below, enable very quick and easy connection changes.

Trench (with mulch pushed aside for photo)

At one stage I laid slotted ag pipe under the mulch inside a trench in an area of the garden where the soil was too permeable for an ordinary trench, and poked the end of the greywater hose into the end of the ag pipe. Don't do that! For some reason the ag pipe seemed to obstruct the flow of the water such that almost all the water soaked in right at the start end of the trench. (If you start with un-slotted ag pipe, and just put in holes where you want the water to go, this might work well though.)

To cope with fluctuations in the quantity of used shower water available, I suggest having the length of the trench short enough for the water to reach the end of the trench with about 30L of water (a 3 minute shower), but make it deep enough so that the trench does not overflow after the longest shower you are ever likely to have.

Alternative trench layouts...
For watering widely spaced fruit trees, for example, it is more practical to have a separate circular trench around each tree (over its root zone), and to have a branched hose layout so that water will go to multiple trenches simultaneously. Unless you are very lucky with your gradients, it is unlikely that you will get an even distribution of the water using just "Y" or "T" junctions to split one hose into 2, then into 4 (or more). However, if the water distribution is sufficiently even for your needs, this is certainly the simplest way to go.

A more even distribution can be obtained by using some sort of buffer tank as a splitter box. Basically, this is any sort of container with a capacity of about 30-50L, and with permanently-open outlet fittings in its base. A hose is attached to each outlet, and each hose takes the water to one of the circular trenches. Provided that the water flows into the buffer tank/splitter box faster than it can flow out the outlet hoses, this will give an even distribution of water to each tree. See this page (or use the tab at the top of the page) for one way of constructing a splitter box.

Depending on your garden layout, gradient, and relative water needs of your plants, you can probably put together a design that combines the above three variations to advantage. For example, one outlet from a splitter box could go to one large tree, another of the outlets could be branched into two to water two small trees that need less water and are reasonably close together, a third could go to a straight trench along a row of rose bushes, etc.

Dripper hoses...
This method gives a good deal of control over where the water goes, and can give a more even distribution, particularly with permeable soils. Since the flow of water from dripper hoses is slower than the flow of water from your pump is likely to be, you'll need some sort of buffer tank to temporarily hold the used shower water. Paired with a buffer tank of suitable size, a dripper hose setup can cope with wide fluctuations in the quantity of shower greywater available on any particular day. By "dripper hose", I don't mean the special-purpose dripper hoses sold for use with greywater - I've no experience of using them. I just mean any ordinary sort of irrigation hose or greywater hose with holes in it.

Note that the buffer tank is just used as a buffer, not as a storage tank. Make sure that at least one outlet is always open so that the water starts flowing out of the tank as soon as there is some water in it.

What I've done...
When the greywater is pumped out of the bathroom, it travels via a 19mm poly hose (the ordinary inexpensive black stuff normally used for garden irrigation) to the top of a raised buffer tank (an ordinary 200L poly tank). The outlet at the bottom of the tank branches into 4 separate distribution hoses, each with an inline tap. The tank outlet is higher than each of the areas being watered, so I can use gravity to do the distribution work through whichever distribution hose has its inline tap open that day.

The distribution hoses are low-quality ribbed greywater hoses - the sort sold for use with laundry greywater. When I first began using these I used a corkboard push pin to put fine holes between the ribs adjacent to the plants I wanted to water. This worked well for some weeks, but then the holes started clogging up and needed redoing. It's currently wet and wintry so I'm not using any greywater on my garden at the moment, but when I need to use it again, I'll be putting much larger holes in the hoses - I'm thinking that a small screwdriver or a metal skewer should make large enough holes. In the photo below, the distribution hose is exposed because its not currently in use, but once Spring arrives and this bed is planted, the soil and hose will be covered with mulch.

After all the greywater has emptied out of the buffer tank, I decide which area of the garden should be watered the next day and switch the inline taps accordingly. On days when there is a greater than usual volume of used shower water, I leave 2 of the inline taps open so that 2 areas of the garden are watered simultaneously that day. If nothing needs watering, I simply take the Big Bucket out of the shower alcove and let the shower water run straight down the bathroom drain

My distribution hoses are each 10m long. That length works well with the amount of water from 2 showers per day, and with all of one day's water going through the same distribution hose to one area of the garden. If you have a larger family (or longer showers), you can adjust for this by having longer distribution hoses over a larger area, or by having 2 or more inline taps open simultaneously. You might also wish to have a greater number of outlets from the buffer tank and/or have one or more outlet hoses that do not have any holes until they reach a particular part of the garden, but then might branch into two or more hoses that do have holes, possibly with the branching controlled by inline taps (unless you want to water these areas simultaneously).

Other alternatives...
When Arthur pumps the shower water out of the bathroom it runs through a hose to a water spike. This takes water deep under the surface to the root zone of a tree, for example. Each day he moves the spike to a different tree, in rotation. This is possibly the simplest distribution method for those who have only a small quantity of shower greywater each day. However, Arthur reports that the action of pushing the spike into the ground sometimes causes it to clog with soil.

Reed bed filtration
I've not experimented with passing greywater through reed beds as a means of filtering and cleaning the water. I'm not sure that there would be a lot of point in me doing that since my system uses the greywater immediately. Besides, I've always imagined you'd need more space than I have to construct a reed bed. Anyway, there is a reed bed type of system here that caught my attention. The vertical bathtub system would not need that much space, and I like the look of it.

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