New pressure washer advice

[carbon]

Parts are still available for that particular pump. Its ok for a short duration to recirculate the water, but doing so increases the water temperature inside the pump. Turning off the machine is better for the life of the pump internals.
Adding an external detergent injector after the unloader valve is an easy way to add detergent to the water, fitting this after the pump means no detergent should enter the pump and remote operation of adding detergent is possible from the end of the outlet hose.

 

[julianf]

A bit of a tangent, but I've never understood how pressure washers add detergent on the high pressure side. Id assumed it was just by a Venturi unit right at the end?

 

[carbon]

Id assumed it was just by a Venturi unit right at the end?

The venturi is usually placed on the outlet of the machine, some unloader valves have the venturi incorporated into them. The problem with venturi injectors is they work better with shorter hose lengths. Generally with a 3/8" id hose 20-25m is about as long a hose that these will work with, but it also depends on the pressure, flow, trigger and low pressure device fitted. Smaller hoses cause more problems and 10m may be the length limit for 1/4" id hose. Some of the snow foam lance attachments have the venturi in the unit itself but these will have a bottle or small hose fitted to the lance for detergent so hose length, bore size etc doesn't have any effect on the detergent application rate.

 

[Guzrik]

The venturi is usually placed on the outlet of the machine, some unloader valves have the venturi incorporated into them. The problem with venturi injectors is they work better with shorter hose lengths. Generally with a 3/8" id hose 20-25m is about as long a hose that these will work with, but it also depends on the pressure, flow, trigger and low pressure device fitted. Smaller hoses cause more problems and 10m may be the length limit for 1/4" id hose. Some of the snow foam lance attachments have the venturi in the unit itself but these will have a bottle or small hose fitted to the lance for detergent so hose length, bore size etc doesn't have any effect on the detergent application rate.

Thanks, I never realised this but now it makes sense to me.
I have a ten meter 1/4" hose and ever since the soap injector didn't work as well as before, never knew why.
I supose there is a checkvalve between venturi and soap flask so the flask is not pressurised when the trigger is released?

 

[carbon]

I supose there is a checkvalve between venturi and soap flask so the flask is not pressurised when the trigger is released?

Yes it also prevents it doing it when operating at high pressure.
If the machine is used regularly then this works ok. If the machine is only used occasionally then detergent can stick the check valve together, as a precaution replace the detergent with water and operate it on low pressure to flush detergent from the check valve

 

[julianf]

Yes it also prevents it doing it when operating at high pressure

So the soap only operates when the motor is not running?

Ie all the soap attachments for pressure washers are actually just "garden hose" attachments and not pressure units at all?

I assumed they worked with the high pressure flow?

 

[carbon]

So the soap only operates when the motor is not running?

No the motor needs to be running to generate the pressure through the restriction in the injector but there has to be a low pressure device on the lance, either a twin lance with two nozzles, one large one for low pressure and a high pressure nozzle. A foam lance or adjustable nozzle to allow low pressure operation.

 

[Ruffian]

I went the other direction and found a "parker brand" petrol pressure washer.

It's heavily Chinese but for the price it's agricultural, clunky 4 stroke weighty but awesome.

Certainly a proper hit of power behind it and great for washing the bikes off when no electric.

Got it when was on special and was only £170.

 

[Guzrik]

So the soap only operates when the motor is not running?

Ie all the soap attachments for pressure washers are actually just "garden hose" attachments and not pressure units at all?

I assumed they worked with the high pressure flow?

At low pressure the venturi creates a vacuum, and the outside atmosphere pushes the soap into the line.
Flowrate is always the same, closing the opening at the end of the hose/gun creates the pressure, and the vacuum changes to an overpressure stopping the soap.

 

[Guzrik]

Now I learned, the motor is 7.5kW and I only have 3x16A.
It has a star delta switch but I wonder if I can run it?

 

[Guzrik]

I bougth this one

As soon I put water on is flows out of a small tube at the end of the pump.
Is this normal?

Furthermore the microswitch to switch of doesn't work so I am afraid to put my hose on as the pump won't stop at pressure and blow up my hose?
Is rotation direction important on one of these?

It is a Alto pump so related to Nilfisk I belief? NP5 19.20

 

[carbon]

The water leaking from the red fitting isn't correct. It is a thermal device that fails if the water in the pump gets to hot when left in bypass for to long. Ideally fit a new replacement but it can be blanked as a temporary measure. Not every manufacturer uses that item.

The system needs to see that water has reached the desired pressure to operate the unloader valve and the pressure switch should operate to stop the motor. With no hose it wont stop on its own. If the micro switch has failed as long as the unloader valve works then its possible to use it but don't leave it in bypass for long as the water circulating through the pump will get warm. If it gets to warm the pump seals can fail.

 

[Guzrik]

Thanks (again), as a "temporary " measure I will leave it leaking if that is no problem? I will repair the switch fist and see if I can get it to switch off.
But for now I will try the hose and gun first.

 

[carbon]

Remove the leaking thermal device and blank the port, as its leaking water from the pump it can also draw air into the pump if the water supply is insufficient.
Inlet port should be 1/2" bsp