Thread: Drainage Pump

Originally Posted by Flyboy

G'day all,

Need your help (yet again) with a drainage problem I've got. Our problem is the backyard floods. After the last lot of rain we had over 3 days, I figure there was around 10000l sitting on the ground and this is nowhere near the worst I have seen it. There's nowhere I can run some agline to.

The plan at the moment is to put in a sump pump. The water needs to be pumped over a distance of 30m up to a height of around 4m. Ideally, I would use a 12v automatic pump, doesn't need to pump out at a great rate, probably around 3-400 l/hr would be enough. I've sourced a power supply from Jaycar which is rated at 12v 5 amps.

The main problem is the only suitable pump I've been able to find is a marine bilge pump, and would have preferred something that was made specifically for this purpose. I've rang around and everything else is either 240v or 12v with no automatic float switch.

All ideas welcome

Hi, you'll find that most 12v submersible pumps are sold as marine or bilge pumps.

However that should not stop you from using them, after water is water, whether it is "marine" or agricultural.

Have a look here:

http://cgi.ebay.com.au/Brand-NEW-12V...QQcmdZViewItem

You may be able to utilise the drainage depression you have an get an inground storage tank installed, fed from drains in the backyard, and run a pump from that into your hoses, laundry etc

All dependant on needs, access and $$ though

Thanks for the replies. An inground tank is probably a bit outside the budget at the moment, but not a bad idea.

No worries, Big Shed, just needed to hear it would work from someone else

The next question I have is about pump performance. Seeing as though these pumps weren't made for pumping long distances the guys at the boat shop have no idea how they'll perform. The spec sheet for the pump I'm looking at says it'll pump to a height of 4m but it's a bit marginal.

My 2 choices are :

1. Pump the water 30m to a height of 4m then down to the outlet at about 2.5m. Once the water gets over the 4m 'hump', should I get the same flow rate as I would pumping to 2.5m?

2. Pump the water a longer 60m to a height of 2.5m. How much effect does the extra distance have on pump performance?

Also, if running a wider pipe from the pump would increase the back pressure in the line reducing the height you can pump to, would using a narrower pipe allow you to pump to a height higher than rated?

Thanks

I had an automatic pump installed a few years ago which I think would do your job.Unfortunately it's 240v. I think it was bought from Hardware and General in Brookvale.
If I wanted to get the finer details of performance I would go to a manufacturer.Probably most in China so no good for you but Davey Pumps are still around and they are local and would be able to help you.

Going that distance, at that head, I would suggest spending some decent $$ and doing it once, with a pump that will cope.
Bilge pumps are only really designed to pump short distances, and not for extended periods.

Their performance drops dramatically, as both the run & the head increase.
30m long piping holds quite a lot of water, and the weight of this water will be pushing back at the pump outlet.

It is better to pump 4m vertical, than it is to pump 4m high along a 1:7 grade - you'll have 8 times the water weight back-pressing on the pump.

If you get 10,000L in there, and the pump is struggling, it will take days to clear.


If you want a real budget option, scour the classifieds & garage sales for a 2nd hand pool or spa pump.


If I were in your shoes, I'd be looking at something like this:
http://www.duralirrigation.com.au/on...vigationID=577

You can also get them with automatic float switches (not sure if it's Davey or Onga that have these commonly available on submersible pumps).

EDIT> just realised the pump in the pic on that page has the float switch on it - it's the yellow plastic box dangling off the cord.

I agree, 10000 litres sounds like a lot. Last week we had about 10000l on the ground after 3 days of rain. But let's say that worst case it rains 3 times as hard and I have to pump 10000l away in a day. That's about 400 l/hr. The smallest DC bilge pump I've found does 2000 l/hr. All the 240v pumps are way more powerful than this and I'd rather not run 240v through the garden unless I have to.

The bilge pump I'm looking at will pump about:
3000 l/hr at 0 head
1200 l/hr at 2.5m head (height of pump outlet)
200 l/hr at 4m head (maximum height I have to pump to)

I presume these were calculated over no distance.

It is better to pump 4m vertical, than it is to pump 4m high along a 1:7 grade - you'll have 8 times the water weight back-pressing on the pump.

This is exactly the kind of stuff I need to find out, but I'm not sure I entirely agree with you. Quite happy to be corrected, though

Say for example I set the pump up so that first it pumped 4m vertically up and then 30m horizontally at 0 slope. Would this work? My uneducated guess is that it would. You'd have the same pump, pumping over roughly the same length pipe to deliver the water to the same point. In that case, if running pipe at 1:7 to the same point didn't work, it would just be the placement of the pipe which stopped this from working, which I can't quite get my head around.

Cheers

If it was me I'd run a very slight slope away so gravity pulls water away rather than the pump pushing it. In the end if it is dead level you are probably going to end up with stagnant water sitting in the pipe as nothing over that distance is likely to remain level. I'd go for 4m up and then away for the same reasons given pushing the water up a long slope. Bilge pumps aren't design to cope with psi in the outlet and thats what you'd be applying. FWIW my experience is limited to boats, and shortest length of pipe up to minimum height for exit was all we ever worked on, and buy a pump three times the size you thought you needed just in case.

I'm not sure a marine bilge pump will really do the job, but go for the recommended pipe size up to your high point and use whatever pipe you like after that providing its no smaller. The bilge pumps are designed to spew out a bit of rubbish but pressure in the pipe does seem to allow flow back through the pump.

You can treat these comments as pretty uninformed, other than read the packet I never got much into the things, once half full of water in a boat you are stuffed anyway, the pump was there for rough weather not disasters. They're pretty handy when you take waves over the front but then its only short runs at a time.

Cheers John.

Are you sure there isn't a storm water line you can tap into? Sounds like your backyard is a bit of a bathtub but your roof storm water must be going somewhere.

Originally Posted by silentC

Are you sure there isn't a storm water line you can tap into? Sounds like your backyard is a bit of a bathtub but your roof storm water must be going somewhere.

Yes, there should be an easement somewhere, along the fence?

Either way best to wait till it dries a bit, and get a machine in to direct the water to one spot where you can control and use it effectively

Flyboy,

A 12V bilge pump won't lift water more than a couple of metres and they won't lift dirty water at all.

What you'll need is something like this http://www.davey.com.au/products/pro...p+%26+Drainage


this http://www.onga.com.au/secure/downlo...fileid=1001546


or this http://drip.com.au/onlinestore/index...igationID=1018

Originally Posted by mixin

It is better to pump 4m vertical, than it is to pump 4m high along a 1:7 grade - you'll have 8 times the water weight back-pressing on the pump.

Head and pipe drag against flow are the only factors.
The pressure at any point is controlled by head not linear length.

Keeping it simple the pump works against head and pipe drag.
Thinner pipes have more drag.
Longer pipes have more drag.
Elbows add extra drag far greater than straight pipe.

AFAIK, the closest stormwater pipe is where I'm pumping to (actually, it's the overflow for the rainwater tank). The problem is our yard backs on to bushland at the bottom of a valley, and the council haven't really done anything about removing stormwater.

I wanted to avoid a 240v pump as I'm not that keen on running 240v under water.

Thanks David G, that was exactly what I needed to know. Found out that the pump I'm looking at is rated at 5.6 psi and looked up a website about pipe drag, I won't bore you all the details, but it reckons I'll get about a 0.5 psi drop over 60m with no slope. Pumping the long way round (60m to a head of 2.5m) should be ok, but taking the short cut (30m to 4m head then back down to 2.5m) will be touch and go.

Might buy the pump the next size up just to be sure

G'day Flyboy,
We live (water wise) with a 240V pump down a 40 metre well/bore/ water supply.
Safe as houses.......the seal on the electrics (it is a Davey pump) has never given up.

AFAIK, the closest stormwater pipe is where I'm pumping to (actually, it's the overflow for the rainwater tank). The problem is our yard backs on to bushland at the bottom of a valley, and the council haven't really done anything about removing stormwater.

Where do your downpipes go?