Ideal 'flow rate' per minute

Green Pro Clean Ltd · Jan 29, 2016

When i first started seeking advice on WFP setups some years ago I recall a forum member telling me that the ideal flow rate to ensure a clean window was 1 liter per minute.

Does anyone know if there is an actuall science to the math?

1 liter per min would give a good 8.3 hours of work time off my 500 liter tank. /emoticons/smile.png

Dave B · Jan 29, 2016

I don't measure my flow but if it goes a couple of inches before it starts to drop then that is perfect flow for me

Just a trickle

Green Pro Clean Ltd · Jan 29, 2016

No offence @daveyboy1 was looking to see if any of our techy lads had an actuall scientific answer not just personal opinions. As i said no offence.

Dave B · Jan 29, 2016

No worries

I reckon that figure was arrived at by trial and error to see what works best

Don't know how you would work it out scientifically

Jonathan Sanderson · Jan 30, 2016

It's al based on preference.

As davey has said, there is variables.

What size jets do you use, what flow rate is your pump etc.

There is no scientific calculation as to how much flow rate is needed to clean a window. A slow flow rate can be used, but you will need to spend more time rinsing and scrubbing the glass.

If you use a higher flow rate you can cut down your rinsing time and in some cases actually save water.

I've known guys use 0.3 litres per minute with 1mill jets, and some guys use 3 mill jets and have about 5 litres per minute. Both can do the same job, but quality and speed can differ.

I use 3 mill jets and get about 2 litres per minute at the brush head, as I feel this is a happy medium between water use, efficiency, and speed.

Andy · Jan 30, 2016

Must be what suits you. The only variables that would make a difference are after the water comes out of the jets. Brush size pressure on glass speed bristles ect. A variable speed controller you can adjust to deliver a Lt per minute out of jets what ever pump etc you have. I must admit it is a interesting question.

Solarpanelcleanington · Jan 30, 2016

Depends on type of glass, speed, brush, phase of the moon. It would be good if we all measure how long it took the pump a litre (through hose and brush) on our standard setting. Maybe.

spruce · Jan 30, 2016

When i first started seeking advice on WFP setups some years ago I recall a forum member telling me that the ideal flow rate to ensure a clean window was 1 liter per minute.
Does anyone know if there is an actuall science to the math?

1 liter per min would give a good 8.3 hours of work time off my 500 liter tank. /emoticons/smile.png

Probably give you twice that amount. I estimate we are only pumping water cleaning residential windows for about 50% of our working day. The remainder is packing, moving and then unpacking, wiping sills, writing out tickets and talking. /emoticons/smile.png

Commercial is probably 75 - 80%.

spruce · Jan 30, 2016

It's al based on preference.
As davey has said, there is variables.

What size jets do you use, what flow rate is your pump etc.

There is no scientific calculation as to how much flow rate is needed to clean a window. A slow flow rate can be used, but you will need to spend more time rinsing and scrubbing the glass.

If you use a higher flow rate you can cut down your rinsing time and in some cases actually save water.

I've known guys use 0.3 litres per minute with 1mill jets, and some guys use 3 mill jets and have about 5 litres per minute. Both can do the same job, but quality and speed can differ.

I use 3 mill jets and get about 2 litres per minute at the brush head, as I feel this is a happy medium between water use, efficiency, and speed.

I think Jonathan has summed this up well.

When we started wfp we had 1/2" garden hose, 3mm jets, no flow controllers and a 5 liter pump. We got through water like anything. I had a trailer with 375 liters and had another 100 liters in my Suzuki Van.

I was out of water by 3 o'clock most afternoons. I wasted so much water washing the windows, but rinsing was brilliant. I flooded the windows so it made little difference what type of glass it was.

When Williamson's came out with the first Varistreams we bought one. By turning the flow down we were able to save water, but were slower during the day. I had enough water to last another couple of hours without touching the 100 liter backup. But all I was able to do was another 3 houses or so a day, which didn't equate to that much financially.

Since then I have always maintained that a slow flow isn't everything. I needed a reduced washing flow and a fast rinsing flow for optimum results. I used to use 1.5LPM water flow at the jets. It increased to 2 LPM and higher than that now but I haven't measured it. With the 4040 we now have plenty of water so I'm not as stressed about 'wasting' water as I was. I'm back to 2mm jets as I find I can work better with those.

Spring was going to bring out a 2 speed controller which was controlled by remote. They sell them in the States. For me that's an interesting concept. Wash with low flow, press a button and rinse with a fast flow, both user programmed. Not sure how well it would work in practice though.

Trev81 · Jan 30, 2016

I use around 2.3 litres per min with 2mm jets, find this a good flow for working quite quickly and to give a good rinse without standing there for ages. Like others say its what ever suits and also what type of setup your running, for trolleys and people not carrying lots of water then I guess the flow rate needs to be lower to conserve water more.

650L does me about 25/30 homes (a mix of detached and smaller some with connies some without)

dyson123 · Feb 21, 2020

Hi guys, I have a 4.5lpm 100psi pump but I’m only getting 1.25lpm at the jets with the controller on 100.

I have 30m of 8mm OD/ 6m ID on the hose reel and 12m of 6mm OD/5mm ID pole hose with 2mm pencil jets.

Why is the lpm so low and what can be done to increase it?

Thanks chaps

Part Timer · Feb 21, 2020

dyson123 said:
Hi guys, I have a 4.5lpm 100psi pump but I’m only getting 1.25lpm at the jets with the controller on 100.

I have 30m of 8mm OD/ 6m ID on the hose reel and 12m of 6mm OD/5mm ID pole hose with 2mm pencil jets.

Why is the lpm so low and what can be done to increase it?

Thanks chaps

View attachment 19411

Is that per jet or combined?

dyson123 · Feb 21, 2020

Part Timer said:
Is that per jet or combined?

Combined, ran the jets into a measuring jug for 60 seconds.

Part Timer · Feb 21, 2020

Sucking air or pump on the way out is my best guess.

spruce · Feb 21, 2020

dyson123 said:
Hi guys, I have a 4.5lpm 100psi pump but I’m only getting 1.25lpm at the jets with the controller on 100.

I have 30m of 8mm OD/ 6m ID on the hose reel and 12m of 6mm OD/5mm ID pole hose with 2mm pencil jets.

Why is the lpm so low and what can be done to increase it?

Thanks chaps

View attachment 19411

If you remove the 12 meters of pole hose does the flow rate increase?

We have found that there is a noticeable difference with flow rate though 6mm microbore hose when compared to 8mm minibore, especially this winter. One the the biggest flow reducers is flow turbulence inside a coiled hose.

Microbore is half the 'size' of minibore.Your are now adding a length of pole hole which will further restrict flow.

A pump flow rate is given on full pelt with no output restriction. Add restriction and the flow rate drops considerably.

I posted this on another forum 3 years ago

Another poster on this forum couldn't understand why a difference in 2mm hose size (8mm minibore to 6mm microbore) should make a difference in flow. Doug Atkinson from Daqua posted this in reply

It does -------, makes at least 30% reduction in flow

Take a look at this; Added; Sorry this link no longer exists.

http://www.flourmilling.co.uk/water.html

I realise its steel pipe but I see the flow rate difference between 6mm and 8mm bore steel pipe is considerable. At 4 bar the flow through 6mm pipe is 0.022 liters per second. The 8mm pipe its 0.056 liters per sec at the same pressure. So a 6mm tube will only allow fractionally less than 1/2 the volume of water at 4 bar. Our hose coiled up around a hose reel will probably reduce those figures a bit more.

Hot water will have a higher (or is it lower) viscosity (less dense) so will flow better through a smaller diamt hose. So most hot water users happily use microbore hose.

http://www.frca.co.uk/Documents/100308 Physics of flowLR.pdf

Interesting read these 7 pages.

Look at the difference between Laminar flow and Turbulent flow. Once fluid in a tube reaches a certain speed it become turbulent. Once it becomes turbulent it requires 4 times the amount of pressure to double the flow rate. Fluid through hose coiled on hose reels won't be laminar in flow but turbulent.

To calculate the area of a circle the formula is

A = π r2

A 6mm id hose is fractionally more than half the size of an 8mm hose.
A 3mm jet is a little more than twice the size of a 2mm jet.
A 1mm jet is about 1/4 of the size of a 2mm jet.

Pole hose is 2/3rds the size of micrbore. Many years ago Aquadapter (now Exceed Innovations) did an experiment to see if pole hose would be a better alternative to hose reel hose. Nothing came of it. I wasn't sure if this was a sales ploy to sell more pole hose or if it was a genuine experiment.

Marko067 · Feb 21, 2020

I use just 18m of pole hose with my trolley and the difference between 5.5mm ID and 5mm ID pole hose is quite noticeable. Also on occasion I use 25m of 5.5mm ID hose and again the difference in flow is significantly reduced just due to the extra 7m length.

Pjj · Feb 21, 2020

The pump may well be able to pump that volume per muinit but it’s not possible to get that volume through small jets

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Ideal 'flow rate' per minute

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