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Old 13-11-2017, 01:11 AM   #1
Rob D 88
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Karcher K4 Full Control change of gun!

Hi all,

I am looking at changing me Karcher spray gun. I have a K4 full control and I recently purchased a different lance with some better nozzles but unfortunately this did not work properly.

The gun was well under powered and was no where near as effective! I was looking a maybe changing the gun to Mosmatic one but don't want to spend a fortune if the jet wash isn't going to give the maximum pressure!

Has anyone else changed guns on a full control Karcher?

Thanks Rob
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Old 13-11-2017, 02:16 PM   #2
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Having done a fair bit of reading and research into this topic I'll try to summarise what I've learned.

The "power" of the pressure washer has to do with the pressure that is developed at the nozzle. You may be aware that pressure comes about due to resistance to flow. The pump in the PW provides the flow, the nozzle provides the resistance.

Too little resistance (ie a nozzle orifice that's too big) = not enough pressure, and a PW that doesn't seem very powerful.

Too much resistance (ie nozzle orifice too small) and the pump will struggle, it may stop and start intermittently if the machine detects too high a back pressure. No use either!

What you need is the right size of nozzle - erring slightly on the side of caution (better to lose a little pressure rather than put unneeded strain on the pump). Have a look at this (PDF link) for a bit more detail and a handy lookup table. According to the Karcher product page (and specifically the specifications on page 14 of this PDF), your K4 is rated for 6.3 litres per minute at 11MPa, or 110 bar.

Using the table linked above, on the 110 bar column the flow rate of 6.3 litres per minute would suggest a nozzle between a 0.25 and 0.3. Note that none of this has anything to do with the gun you are using - it's all about the size of the nozzle. It depends on the lance you're using but you might be able to change the nozzle size (they are frequently available separately, sometimes with a quick release and sometimes with a thread).

If you can post a picture of the new lance & gun, I can try and suggest the best way to update the nozzle. It would also be well worth going back to the place you bought it from and asking them what nozzle size it is. My guess is that you've got a 0.35 or 0.4 that is reducing the pressure and hence effective power of your machine.
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Old 13-11-2017, 03:15 PM   #3
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[QUOTE=steelghost;5402079]Having done a fair bit of reading and research into this topic I'll try to summarise what I've learned.

SteelGhost...

Thank you for replying!

You are right, but I did do some research into this before hand too. What I found was that a Karcher K4's should be at about nozzle 0.40, this is what I got so you are right. However. I did speak with the shop and he did say the K4 is normally around a 0.40 nozzle as well.

He could be wrong and it looks like he is, I got a quick release nozzle set up so I might just order a 0.30 or 0.35 and see if it helps. They are only a fiver!

What do you think?

Thanks Rob
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Old 13-11-2017, 03:36 PM   #4
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Hi Rob - if you have a QR nozzle setup then you have a very quick way to test / resolve the situation. I would go to a 0.30 nozzle in the first instance - based on the flow / pressure table, I think a 0.35 would still be a bit big.

Worth noting you can get a set of all the angles for £12, might be better value than buying individually even if you only use the 15, 25 and 40 degree ones.
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Old 13-11-2017, 04:07 PM   #5
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Quote:
Originally Posted by steelghost View Post
Hi Rob - if you have a QR nozzle setup then you have a very quick way to test / resolve the situation. I would go to a 0.30 nozzle in the first instance - based on the flow / pressure table, I think a 0.35 would still be a bit big.

Worth noting you can get a set of all the angles for £12, might be better value than buying individually even if you only use the 15, 25 and 40 degree ones.
Yep,

I will order some later today!

Thanks SteelGhost, I will let you know how I get on!
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Old 13-11-2017, 10:16 PM   #6
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Hi rob could post some pics of your gun and how attach from the hose to the gun please?
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Old 14-11-2017, 01:35 AM   #7
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Quote:
Originally Posted by bigbruiser View Post
Hi rob could post some pics of your gun and how attach from the hose to the gun please?
Hi I can't get some pics right now but it's the Karcher quick release system. Standard on all fairly new Karchers.

Thanks
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Old 19-11-2017, 08:24 PM   #8
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So today I got to try out the lance with the new size nozzles.

I can confirm Steelghost was 100% correct. The lance with the 030 nozzles was fantastic and back to full pressure!

Makes the pressure washer better to use as the fan angle is perfect. I got 0,15,25 & 40...

Thanks SG.
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Old 19-11-2017, 08:55 PM   #9
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Good stuff, glad you got it sorted. Btw the larger nozzle is a useful thing to have when you want a bit more of a gentle rinse rather than FULL POWAR!
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Old 20-11-2017, 12:24 AM   #10
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Rob what brand of gun did you get? i got the Jinkang High Pressure Washer Gun off amazon but as soon as let off the trigger the K4 pump pulsed on and off and did not sound well then water started spraying all over from the brass fittings, sent it back
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