Pressure washer flattens hose

Merlin5 · 31 Jul 2019 at 21:54

I used my new Nilfisk today to wash my car. The thing is, after a few seconds the hose goes flat and the water pressure gets weak. So it took longer to do the job.

After not using the machine for a minute or so the hose reinflates, I get a few more seconds of full pressure and then the hose goes flat again. It's a new hose I bought last year and I'm running it about 30 feet from the tap in my garden to the front of the house.

I made sure to untwist all kinks along the length. Could it be the wrong gauge hose as I think it's slightly narrower than standard?

NoobCannon · 31 Jul 2019 at 22:03

Assume your talking about the garden hose rather than the pressure hose.

Can only think that your tap isn't supplying enough water, try cutting a few mtrs off and trying the washer on the now shorter hose. Or try your old hose if you still have

Quartz · 31 Jul 2019 at 22:18

Turn the tap on full.

jpaul · 31 Jul 2019 at 22:18

we discussed them in the car clean thread recently .. is it inadvertently set to suck water, like from a bucket ... but I can't see how it can flatten the inlet water hose.

the pressure hoze is too rigid to be flattened, but a problem in the machine can cause the machine to deliver water intermittently.
I recently posted a tear-down of the a karcher I had to fix, where a sticky pressure relief valve caused an intermittent delivery.
http://www.epowerwash.com/wp/archives/631

Quartz · 31 Jul 2019 at 22:24

You mention the hose being narrow: is it narrower than the pipe? A pressure washer can only deliver the water it receives and if it pushes the water out at a greater rate than it receives it will indeed create a vacuum.

BTW your stopcock is fully open (less a quarter turn), isn't it?

Merlin5 · 31 Jul 2019 at 22:32

NoobCannon said:
Assume your talking about the garden hose rather than the pressure hose.

Can only think that your tap isn't supplying enough water, try cutting a few mtrs off and trying the washer on the now shorter hose. Or try your old hose if you still have

Yes, the garden hose. That's a good idea, I'll try a shorter piece.

I've definitely had enough water pressure before though (few years ago) and was able to wash with no issues with my old Karcher. I think it was with my old hose that I don't have anymore. I remember last year the hose also flattened before my Karcher broke and I'm fairly it was this new hose.

Merlin5 · 31 Jul 2019 at 22:54

Quartz said:
You mention the hose being narrow: is it narrower than the pipe? A pressure washer can only deliver the water it receives and if it pushes the water out at a greater rate than it receives it will indeed create a vacuum.

BTW your stopcock is fully open (less a quarter turn), isn't it?

Yes, tap fully on. I think you're right, that a vacuum is being created and flattening the hose. It probably is the wrong gauge hose. It doesn't appear to be narrower than the pipe, though it still might be that that hose needs to be wider. But see what you think from my photo.
And I measured the hose to be just 1.5 cm wide. Perhaps I need one that is 2cm+?

Mark M · 31 Jul 2019 at 23:09

That hose looks a bit odd but I’m in bed so don’t have mine to hand to measure. Can you borrow a neighbours hose to try?

jpaul · 31 Jul 2019 at 23:24

hose is fine .. I have a 50m hozelock starter set driving my karcher of that dia. 12.5mm/1/2" internal ... you could check how long it takes to fill a bucket.
they work by pulsing the water in squirts .. so the inlet flow rate doesn't have to be that great 10L/min is fine.

Merlin5 · 31 Jul 2019 at 23:31

jpaul said:
hose is fine .. I have a 50m hozelock starter set driving my karcher of that dia. 12.5mm/1/2" internal ... you could check how long it takes to fill a bucket.
they work by pulsing the water in squirts .. so the inlet flow rate doesn't have to be that great 10L/min is fine.

Hmm, well if it's not the hose then I'm stuck. I'm pretty sure I used my old machine without any drop in pressure. Maybe the outside tap needs replacing. I get plenty of water pressure indoors. I'll fill a bucket and see how long it takes.

chaparral · 1 Aug 2019 at 05:16

Merlin5 said:
Hmm, well if it's not the hose then I'm stuck. I'm pretty sure I used my old machine without any drop in pressure. Maybe the outside tap needs replacing. I get plenty of water pressure indoors. I'll fill a bucket and see how long it takes.

It not enough water flow that causing this or the side walls on the garden hose are not strong enough (I.E cheap hose) so the suction of the pressure inlet pump is sucking the hose walls in
Make sure nothing in the house is using water at the same time (Washing machine, Dish washer, Taps, Toilets, etc)

And use a short hose as possible to feed the pressure washer..

Merlin5 · 1 Aug 2019 at 09:54

chaparral said:
It not enough water flow that causing this or the side walls on the garden hose are not strong enough (I.E cheap hose) so the suction of the pressure inlet pump is sucking the hose walls in
Make sure nothing in the house is using water at the same time (Washing machine, Dish washer, Taps, Toilets, etc)

And use a short hose as possible to feed the pressure washer..

Yeah, it could certainly be that the hose is collapsing because the side walls are getting sucked in. If so, can you recommend a hose that is very strong, that maybe I could pick up at Homebase, B&Q or Amazon?

Psycho Sonny · 1 Aug 2019 at 10:49

Merlin5 said:
Yeah, it could certainly be that the hose is collapsing because the side walls are getting sucked in. If so, can you recommend a hose that is very strong, that maybe I could pick up at Homebase, B&Q or Amazon?

hozelock do one which you can drive a car over it and it won't flatten.

go onto official hozelock website and see their range. then pick one and then order from amazon or ebay.

https://www.hozelock.com/product/super-tricoflex-ultimate/

30 year guarantee - should last forever

i have this one and it's also 50m i believe. yes it's long but it should do anything i ever require it too and last forever. wasn't cheap but if you think about the fact you will only ever need to buy 1 hose for life it is worth it.

Merlin5 · 1 Aug 2019 at 21:08

Thanks Psycho Sonny. Well I've done some testing today and a short video. First thing to say is that there's nothing wrong with my water pressure, which I'm happy about.

I tested two hoses. The first hose in the video is an even narrower gauge, an inexpensive Homebase own brand, about 1cm wide, and after testing with a standard multi pattern spray gun that came with that hose, it also worked really good with the Nilfisk while coiled up on the reel and there's 10 metres of it. Full pressure, no collapsing of the hose.

Then I tested with the hose I used yesterday which is 25m long and couldn't get much water to come out of it today. I then cut about a 6 foot length from it and tested that and it worked flawlessly with the Nilfisk with no reduction of pressure or flattening of the hose.

I'm not sure why it doesn't work properly when the full length is connected, especially considering my other narrower hose works with all 10 metres.

Could it be that 25m of hose is simply too long?

Participant · 2 Aug 2019 at 06:26

All other things being equal, the longer the pipe the lower the flow rate, due to resistance.

25m of hose is obviously reducing flow sufficiently that the pw creates a vacuum and collapses the hose.

NoobCannon · 2 Aug 2019 at 06:48

I would say that the 25m of hose is just poor quality, shouldn't be collapsing.

Bin it and buy a hoselock one or something from homebase or b and q, if it happens again take it straight back for return and try different one

jpaul · 2 Aug 2019 at 08:24

he hasn't confirmed what the internal diamter is but likely to be 1/2" since the fittings look 'normal'
but the hose quality does not play, if the nifisk is pulling more water than can be supplied that problem/vacuum will remain even if the hose has more integrity.

.. would be interesting to calculate incoming pressure .. I have 40litres min@ 1bar, hous eincoming, and with 50m hoze worked fine. (boilers often show pressure - no ?)

the machines use water for cooling motor too, so interruptions are bad, hence I always prime.
also shouldn't play the jet on a hoze - they can damage them. I wrecked the clearcoat on a car bonnet ... and they say don't spray close on car tyres.

Psycho Sonny · 2 Aug 2019 at 12:10

my 50m hose has no issues

Bluecube · 2 Aug 2019 at 12:32

If the OP continually has issues with a lack of water being supplied to the pressure washer then try filling up a large bucket with water and putting a short hose from the bucket to the pressure washer. I’m not sure if it’ll work with a wee pressure washer but it should suck the water out of the bucket.

Merlin5 · 2 Aug 2019 at 12:33

So guys, it's obviously still a question of either the hose or the water pressure. From my video, seeing the water directly coming out the tap, does it look like there's enough flow that should be able to keep up with 25m of hose? If not, there's no way for me to use my pressure washer for my car or front of house as I only have an outside tap in the garden. Or would a plumber be able to increase my water pressure?

I just spoke to Nilfisk and was told they recommend 15m maximum hose length but someone is going to call me to confirm that. But jpaul is running 50m, so surely it can do 25m.