The theoretical and practical limit on hose length when pressure washing is different. I’m going to assume you mean practical limit when asking this question.
With a 1/2″ hose and flow of 2 GPM, theoretically, on flat ground, the limit is close to 10 miles. But there would be 0 PSI to clean your car, so that’s not very practical.
The practical hose length limit is:
- 200-ft. Assuming the hose and pressure unit are at the same elevation. And you’re on a relatively straight line of sight to the pressure unit. You could go well beyond 200-ft but it quickly become more and more risk of hose damage and why can’t you just get closer to the surface your cleaning?
- However, there is 1 catch… Just as sucking soda through a 6-ft straw is harder than a 6-inch straw a longer hose will have troubles sucking the detergent/soap through that length of hose.
Let’s explore this a little more:
Why would length of hose effect pressure cleaning?
Common Answer 1
Because losses from friction in the hose (energy losses)… In reality, pressure losses are tiny in comparison to the overall pressures. Less than 5% (links to chart showing pressure loses in hoses/pipes) of pressure is lost over 1000-ft hose.
Common Answer 2
Because the pump just can’t push the water that far. It isn’t powerful enough to provide it with that much energy.
Now we’re getting somewhere. But first, when it comes to energy, we need to know mass of water in the hose. Here’s the volume (easy to convert to mass) of water within different length 1/4-inch diameter pressure hose:
- 1,000 ft hose: 9.65 liters (9.65 kg)
- 150 ft hose: 1.45 liters (1.45 kg)
- 25 ft hose: 0.24 liters (240 g)
A lot less water in the hose than you thought, right?
In terms of pressure washing, the biggest factor in length of hose you can use is elevation…
Do you need to park your truck and pressure washer at the bottom of a hill and then walk up the hill with the pressure wand to power wash?
That’s when hose length limit is much, much less.
- A 55 PSI mains water line with garden hose connected to the tap and walked up a 125-ft (38m) hill will have no water at the top. 55 PSI isn’t enough (energy/volume) to make it out the end of the hose at that height difference.
Annoyance of extra long hoses when pressure washing (even on flat surfaces):
Let’s say you’re using a light-duty electric pressure washer with a 1.5 GPM flow rate. Once you pull the trigger to start washing you’ll have to wait for the water to reach you. The longer the hose the longer you’ll have to wait. This only applies when you start the job.