Monday, May 2, 2011

Recycling Grey Water for the Garden

The other thing the Met Office said about April was that it was also the driest April for many years, with some parts of the UK receiving only 2mm of rain.

Despite having bought a second water butt for the garden last year to collect rain water, it still wasn't enough this month.

We've previously filled the water butt using saved bath water, but it was a troublesome process, and the cheap drill powered pump I had wasn't very good.  In short, it was a... pain in the butt :D.

With more dry weather forecast, it was time to do some bodging...

First of all, you have to collect your grey water.  This is water that isn't full of bits (mud, rocks, etc) or full of chemicals or organic matter.  So water from the kitchen is no good (contains fats and food bits and so on).  Washing machine water can be ok, but often has too much soap, fabric conditioner or even bleach in it.  Used bath water is fine.  Just don't use any bubble bath, bath salt, or go mad with the shower gel and shampoo or conditioner.  The plants don't mind a little bit of soap.

Then you need to catch all the hair and bits of fluff in the water, as the pump won't like it (even with an inlet filter) and you don't want to clog the water butt or hoses either. 

The missus had this handy tool, just for the job.
Dunno if you can get them here, as she bought this one at a 100 Yen shop in Japan, where they are very common bathroom accessories.  You can easily make one with a coat hanger and a bit of old net curtain though.

Incidentally, in Japan, it's actually quite common to recycle bath water into the washing machine for the wash cycle, as the soap powder will suspend the dirt in the water anyway.  Clean water is only needed for the rinse cycle.

Next, you need a water pump.  I'd been looking around for something better than the drill pump (a water pump you attach to a cordless electric drill).  I found this new one by the garden hose makers, Hozelock.
It's designed to be used in a water butt to power hose pipes and sprinklers and so on.  It also says you can use it for emptying small paddling pools, and recycling bath water.  It seems to retail for £70, but with a bit of shopping around, I managed to pick it up for £52.
Water is sucked up from the bottom of the unit through a removable foam in-let filter that catches medium sized (1mm) particles and hair. In the screw-on hose adaptor at the top, it has a finer mesh outlet filter to catch particles as small as maybe 0.2mm in size.  You need to use the fine filter if you're using the company's miniature irrigation system that drip feeds plants, or a hose fitting that has small spray holes that could get clogged.  If you're using ordinary hose pipe fittings then you can take the fine filter out to get more flow.

The water in our water butt has bits in it anyway, and is only used with a watering can tap or jet hose, so I took the fine filter out.

I rigged up the hose outside, cable tying it to some big electrical cable clips I hammered into the wall.  I then used a bit of string to hang the coiled up end loop outside the bathroom window, for when we're not using the hose.

The other end is just coiled up under one of the solar panels at the base of the wall.

When we need to pump water, I just un-roll the bottom end and stick it in the water butt, securing the pipe with a brick... useful things bricks. :D

Then I pull up the other end (using the string from inside), un-roll, and plug it into the pump, which sits in the bath.  The pump uses normal Hozelock click-fit connectors, so you can use any normal hose.

The pump is designed to be completely or partially submerged, with the 10m water proof rubber cable going off to the mains remotely.

Make sure you use a RCD breaker on the socket!  Don't sit in the bath (or pool) while using the pump, just in case... O_o
Then it's just a case of remotely turning the power on.  It draws about 300W, so I ran it from the solar power in the computer room.

The pump proved to be very efficient, quiet and fast.  It emptied the bath of about 100 litres of water in 2-3 minutes, and it had enough pressure (1.1 bar / 16 psi) to ensure that the old hose, that has some kinks in it, opened up and worked beautifully.


The only thing that was a bit annoying was that the pump has a small hole on the side of the body, which sprays a jet of water out sideways, while working.  This is normal as it's a "vent" to allow air to escape from the pump (part of its self-priming function).  That's ok, when it's in a water butt, but it splashed water around the top of the bath tub when the water level got below the height of the hole.  Some fettling may be required...  A small cowl, or summat, to tame the (quite violent) jet that squirts out.

The pump has 2mm high "feet", and this allows it to suck up water right to the last couple of millimetres of water in the tub, especially if you position it over the bath plug.  Very good.  They make another pump which is intended for clearing floods, but it can't work in less than about 75mm of water... No good for draining a bath tub!

This water butt pump doesn't have an automatic float cut-off, so you need to watch it, and turn it off as soon as the water has run out, as running the pump dry will damage it.  Ideally, you should turn it off just as it is about to start "gurgling" at the bottom of the bath.

If using it in a water butt, they recommend standing the pump on a couple of bricks at the bottom of the tank, so that it is clear of the worst of the sediment that collects at the bottom.

Given that we have grey water available every day, and the pump only cost a few Pounds more than buying yet another 150 litre water butt, it seemed good value.  And we get the most out of our metered water.

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