small 12v solar pump for septic tank

[taxus]

Hi all,
New to the forum, and I have looked back thru the archives......

I want a small 12v pump to run via a small wet acid battery and pv panel.
It needs to run a small float type switch in our septic tank outlet chamber.
The water is pretty good, as we do not use any harsh chemicals etc.

Can anyone point me in the right  direction for diagrams and components please ?

I have difficulty tracking the ebay item numbers, as they don't seem to link when I try to look them up for reference, perhaps the items have expired ?

Thanks all.


"Greenish" credentials:

Woodburning Rayburn 212, Solartwin flat plate collector and gas condensing boiler - all talking to each other and working well as a team....!

[guydewdney]

what exactly (as a non septic tank owner) are you pumping? clear filtered water? poo?

Try bilge pumps - the small 'rule' ones are quite dirt tolerant.


heres a non ebay shop - just the first one that came up on my search http://www.mailspeedmarine.com/bilge-saltwater-shower-pumps.bhtml

they also will do 'macerator' pumps which will pump raw sewerage.

If these are too big and powerful - what about car washer wiper squirty pumps or coolant circulating pumps? - ebay I'm afraid.

[taxus]

Hi,

its not exactly "poo", but a rather hardcore version of "greywater".
The tank is fed and managed well, so it seems to "digest" happily. The run-off is greywater, which drains into a herringbone "drainage-field" at the end of our garden.
Problem = the current 230v electric pump is running too much water out, and we need to reduce the flow. Cannot find a suitable 230v pump, so looking at 12v dc solar ones.

Ideally a simple kit would do it, best guess a flow rate of no more than 200l/day max ( 3 x showers @ 30l, 1 x kids bath @ 50l, 2 x washing loads @ 20l, 1 x dishwasher load @ 20l......?)

I'm not familiar with such 12v solar systems, so need a simple and "idiot proof" set-up.

Thanks.

[dhaslam]

When you say the mains pump is pumping  out too much liquid  is the reason  lack of control rather than the pump output rate?     Presumably the float switch  on its own allows extra flow when there is  extra water going in, for example when a bath is emptied.     An extra control that incorporates a delay might be a better solution or just  simply a smaller mains pump.     If you have a twin compartment tank  it might be worth considering  diverting part  of the flow back to the first compartment, this is apparently all that the fancy water treatment systems do, apart from a little aeration.   

[guydewdney]

motor speed controller? (such as a fan speed controller for a house ceiling fan)?

[billi]

Hi Taxus

I installed a 12 volt  Rule bilge pump  and a floatswitch  to pump the grey water in that "reed" bed filter
I have no idea how long it will last , but the pump was only 30 euro + 24 for the float  and is connected to a Mains to  12 volt  transformer

http://www.navitron.org.uk/forum/index.php/topic,11269.0.html

on the otherhand  we have one of those "MACERATORS units" for basement bathrooms that are available for small money (have seen them for 150 Euro ) that works fine since 4 years  in our bath

Billi

[billt]

Problem = the current 230v electric pump is running too much water out, and we need to reduce the flow. Cannot find a suitable 230v pump, so looking at 12v dc solar ones.

You might want to rethink that. Trickling small amounts of water into a leach field isn't the best way to treat them. The effluent stays at the near end of the field and exhausts that, while not using the far end of the leach field.

Send a couple of hundred litres of water at once fills the entire leach field and utilises it much more evenly and effectively.

[taxus]

Hi,
The pump is a single speed type, Hozelock pump. it pumps efficiently, but our layout is such that there is little 'fall' from the outlet to the drainage field, so we have to slow up the discharge somehow.
We actually downsized to the current pump, and it's still too energetic. I thought about removing one or two of the impellors....?

A smaller mains pump might be easier, but the 12v solar one appealed for all the right reasons...

We do have a second compartment, but its the site topography thats causing the issues, it's the downhill bit of the flow that only allows a very gentle fall.

We even had quotes for the supply and installation of a digester tank, in excess of £30K in 2008....!

Any suggestions for a very small capacity float switch operated pump greatly appreciated!

Thanks.
  

[Fintray]

I thought about removing one or two of the impellors....?

Probably not a good idea as likely to put the impellor out of balance!
Why not just put a valve on the outlet and restrict the flow that way?

[taxus]

Hi Fintray,  I did'nt think the balance issue through did I....

Won't restricting the flow ( the old hole-punched-in-a-penny trick...) cause the motor to overheat or some such problem...?

[Iain]

Hi
Or just put a "T" in the pump outlet pipe and put a bypass valve in. Return some of the pumped outlet back to the source. Pump not overloaded and outlet flow controllable. Use a gate type valve and then it is very adjustable.
Iain

[Baz]

Centrifugal pumps use more power when delivering high volume low head than low volume to a high head, so restricting the flow should not be a problem.

[tony.]

is a septic tank a hazardous area, i mean with the build up of gases? and if so wouldnt an appropriate ex rated pump be required.

tony

[taxus]

Hi Tony,

Not a problem in this case as it's a completely open system, not air tight either...

Cheers