can a heavy duty water drainage pump be used to water garden

[laurencewithau]

Hi. I have a larger garden, two 1000 litre water tanks joined together and an electric surface mounted water pump. The pump has a 19mm hose attached to it. It shifts 100 litres per minute, because that's the maximum I could find for pumps of that type.
There are agricultural pumps, usually petrol, I believe, that are more powerful and used to drain ponds and so on. My question is whether they can be used with a garden hosepipe attached, in order to water the garden more quickly and thoroughly in the present heatwave. I live in the UK. Do they, for instance, have outlets to which a hosepipe could be attached? Are they perhaps too powerful? I'd be grateful for any advice.

[Rorschach]

100 litres a minute is pretty good going. I would think that you would struggle to get a lot more through a standard hose pipe and the cost of a bigger pump could be expensive for such a short term use.

[dewaltdisney]

Unless I have misunderstood, at 100 litres a minute your tanks will be drained in 20 minutes. Do you really want it drained quicker? I have read it wrong?

DWD

[Someone-Else]

It doesn't matter just how much the LPM is, its what the head height is too.

To expand on that your pump may be able to deliver 100 LPM but only to a head height of 50cm, but at 10cm it may be able to deliver 160 LPM and at 100cm only 60 LPM
All good pump makers will have a "Pump curve" chart / graph which will show you what you need to know.

Some may also suggest you add a sprinkler, sprinklers have what is known as "water demand" (how much water and at what pressure / flow rate" to achieve a specific distance)

You also have to take into consideration pipe diameter and distance and bends.

All of the above can and does affect the flow rate, and assuming you can get 100LPM at the end of the hose then dewaltdisney is not wrong, the tanks will be empty in 20 minutes, but then I wonder how do they get filled?

The easiest option is to "try it and see" its not accurate but for what you are doing I wouldn't worry too much. (But what I have said is true)

I would also suggest you add a float switch to your tank so when the water does get too low, it will switch off the pump. I presume you have IBC's

[laurencewithau]

Hi Rorschach. Thanks for replying.
After posting the question I found out that the flow from the hosepipe when the pump was on was low not because 100 L/M is not very high but because the heat had caused the inner lining of the hosepipe to come away from the outer skin and collapse in on itself so that hardly any water was getting through.
When I replaced it with a spare hose that had not been left out in the sun I got the full flow and was able to water the garden in very little time.
Silly me, but I'd still like to have even more of a flow rate, and the only way to do that, as far as I know, is to use a drainage pump for flooded cellars, ponds and so on.
For instance, there's one on eBay:
Karcher SP 5 Submersible Dirty Water Pump 240v 9500 Flow Rate (l/h). It says that it can be connected to a hose pipe and set to continuous.
So my question still stands: Can i use this pump for garden watering? Thanks again.

[laurencewithau]

Hi Dewaltdisney. Thanks for your reply. I had not thought of that. If I had, even allowing for difference between pump rate and head rate, I think it's called, I would have realised, given how long the water in the tanks was lasting, that there was something wrong.
It's only after reading these replies that it occurred to me that I could not be getting anything like the 100L/M flow rate.
When I examined the hosepipe, seeing how soft it had become, I opened it up and found that the inner lining had melted away from the outer shell and was impeding the flow. Having replaced it, I now find that there is a much stronger jet of water from the hosepipe. But still, I'd like it even stronger, so the question still stands, except that this time I have a particular pump in mind. It's the

Karcher SP 5 Submersible Dirty Water Pump 240v 9500 Flow Rate (l/h). It would fit inside the tank if I enlarged the opening. It takes a hose pipe, I read, and it can be set to continuous flow. So my question is: Why can't I connect it to the 19mm heavy duty hosepipe with 19mm heavy duty nozzle and water the garden? 100 L/M is 6000L/H. The Karcher would give 9500. Am I missing the point? Thanks again.

[laurencewithau]

Hi someone-else. Thanks for your reply. As I have explained in my replies, I made a mistake when I thought I was getting the flow one would expect from a 100L/M pump.
The hosepipe had collapsed internally in the heat and very little water was getting through.
The new hosepipe I installed yesterday gives a much stronger flow, even if, as I understand from your reply, it will be less than 100L/m due to friction and so on. My question is whether I can use the following more powerful pump for watering the garden:

Karcher SP 5 Submersible Dirty Water Pump 240v 9500 Flow Rate (l/h). It is about 1.5 times as powerful as the present pump and it would fit inside one of the tanks if I enlarged the hole. It will take a hosepipe and, with regard to what you said about a float, it has one. Thanks again.

[Someone-Else]

As I last said, for just watering a garden you may as well "try it and see" Since to work it out I would need the hose diameter, its length, the pumps flow rate and its head height and its flow curve.
I am not saying it will not work, i am saying i have no idea what the flow rate will be.

How do the tanks get re filled?

Also I wouldn't suggest the pump you mention, as its a dirty water pump, I am guessing the water for your garden is clean? Dirty water is water with lots of semi / soluble parts floating in it.
You could use a "clean water pump" as they cost less.

[laurencewithau]

Hi someone-else. Thanks very much for the info. The tanks are rainwater filled or topped up with tap water. Yes, I'll look for a clean water pump. Thanks again.