Garden hose for pressure washer too small?

So I received my new WFP and they make it very clear to use a 3/4 size garden hose and nothing smaller. Anyway, I use a 5/8 garden hose for my pressure washer and I’m wondering if that can be a problem? 4gpm. Is it safe? Been having some issues with my pressure washer and trying to trouble shoot. Thanks.

Your talking from water source to machine? Just use what is recommended,

They didn’t recommend anything. Nothing that I noticed at least

You said so here

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Yeah they said so for my WFP. I’m talking about my pressure washer. I’m saying that when I saw them disclose that for the WFP it made me wonder if there is a minimum for the pressure washer

A 4gpm machine must use MINIMUM a 5/8 hose.

Curious about your wfp setup. Why a 3/4 hose? Is that to a filter?

Well I just received a new tucker system and there was a paper clearly stating to not use anything smaller that 3/4. I’ll include a photo

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Ok this is interesting…

I been using 1/2" hose for all my years as feed hose to my 1/4"id pole hose. Works great MOST TIMES. I think what RHG is doing by suggesting 3/4" supply hose is eliminating any chance of weak flow from those odd places that have less volume from the spigot.


Googled “how much more flow between 5/8 and 3/4”

Differing Lengths
Both 5/8- and 3/4-inch hoses come in various lengths. From 25 to 100 feet long, choose the best length for your property. Be aware that a longer hose reduces the water volume expelled. For example, a 5/8-inch hose 25 feet long produces 44 gallons per minute (gpm). The same diameter hose at 100 feet long has a much smaller output at 11 gpm. Because 3/4-inch hoses have a wider mouth, their output for a 100-foot hose is slightly larger at 18 gpm, but the 25-foot hose increases the water flow to a staggering 72 gpm.

Also a calculator to corroborate.

Always give your pump the best chance to succeed, namely more flow.


Now you just confused me big time. If the spigot can only put out 8gpm max, how is a hose going to help produce up to 72 gpm?

Yes, the gpm from the source is what it is. But you dont want to restrict the flow with too small of a hose.

Your original question

Based on: 1) the reference info, 2) the length and diameter of your hose, 3) the gpm of your water source, how would you answer?

If you are rightly aware of saving your pump, go above what is needed so you know you arent restricting flow to it. That’s what I was trying to say.

Yeah, a more useful calculation would be reduction in flow over a given distance. Like if you’re starting with 8gpm at 60psi from the spigot, what will you have for output at the end of 100’ of 5/8" vs 3/4" hose?

Time to do some more googling… :stuck_out_tongue_winking_eye:


The issue with RO systems is that they need a certain amount of pressure to operate efficiently (and their efficiency increases with pressure, up to their rated limit). By using 3/4" hose, you’re limiting the amount of pressure lost from the spigot. Smaller hoses cause a larger reduction in pressure, partly because they force the water to move at a greater velocity. Friction loss increases with velocity.

If you have pretty good tap pressure where you work, 5/8" should be sufficient, especially if you don’t have a long run of it before your RO. I think that the instructions that came with your system are just trying to illustrate that bigger is better, and that you definitely shouldn’t attempt to use 3/8" or 1/2" to feed the membrane.

Regarding your question about your pressure washer, how many gpm’s is it? If 5/8" hose has always fed it enough to work properly, there’s no need to upgrade to a bulkier hose.

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It’s 4gpm