Downstream 1:20 Dilution Ratio

I have a Ridgid 3.0GPM 3300psi pressure washer with a downstream detergent feed on the CAT pump.

This pressure washer, like some others, is preset with a 1:20 dilution ratio. Correct me if I am wrong but am I stuck hunting down detergents / soaps requiring a 1:20 dilution and just putting the injection hose directly into the bottle of concentrated solution?

Many thanks and great Forum you have here!


No…You can use any detergent or chemical you want. If it’s too strong just dilute it with water before down streaming.

Just because it says you’ll get a 1:20 dilution rate doesn’t mean you really do. You can always test it so you know exactly what it’s pulling it.

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Thanks for the quick reply!

My concern isn’t 1:20 being to strong, just the opposite. Most of the detergents I’ve been using are calling for dilutions of 1:5, 1:10. So if the unit is diluting at 1:20 it’s doing so way beyond what the chemicals are calling for.

Zep is however one that does require a 1:20 dilution but I’m not sure how good it is on vinyl siding. If I do use it I take it I would just drop the injection hose into the concentrated bottle, undiluted?

Again, thanks for the quick reply!


Those box store pressure washing detergents are next to useless. Are you a homeowner trying to wash your home or are you trying to start a business?

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Not all detergents or chemicals are a strong enough concentrate to where they can be down streamed. The only thing you really need to down stream is bleach and surfactant. Most of us use 12.5% sh (bleach) and dilute it down before down streaming if need be. If we need a stronger mix we use a 12 volt system. You don’t want to use Zeps on vinyl siding anyways. I believe Zeps is a degreaser. If the detergent you want to use is too weak of a concentrate to down stream you have to look for a different application method such as a pump up sprayer or 12 v pump.

Like Max said any of that big box store stuff is junk. Let us know what you’re trying to clean and we can help or point you toward some info.

The only chemical I buy from the big box stores on a semi regular basis is the ZEP purple degreaser. It works pretty well and I don’t feel like I need a full hazmat suit to use it like some of the others. Other than that I get everything locally or from PT.

Do people normally hop on, ask a question, and never come back? Ya’ll are gracious to help out the newbs!

No, we come back. I sincerely apologize for this egregious delay (understatement) but life managed to get in the way. Any replies are most certainly appreciated! The time someone takes to help is very, very appreciated.




As I pointed out a few moments ago, I sincerely apologize for this gross delay in responding. I’ve had some major issue arise that have swallowed up my time like a Black Hole.

I am only using this for the vinyl siding on my house. I only recently learned last week that my pressure washer (Ridgid RD80702) , although downstream, pre-dilutes at a ratio of 20:1. I was under the impression that if a downstream pump it did not pre-dilute at all. So I have been diluting box store products per the manufactures directions (I.e., 1:10, or 1 part concentrate to 10 parts water) and all along the pressure washer has also been it.

Leary of using bleach but if I do what’s the recommended dilution when it’s already being diluted 20:1?



Beach is what all professional pressure washing contractors use. At least the ones that know what they’re doing.

Think about it like this. You injecting a detergent or chemical into a stream of water so of course it’s going to be diluted.

For bleach you want about 1% hitting your siding. Just try and pull straight bleach if you get the 6% stuff from the store. If it turns the green or black algae brown in about 5 minutes you’re good to go. If it turns it brown in under a minute pre dilute it a little. If straight 6% doesn’t kill the algae go to a pool store and get 12.5% liquid shock. It’s no different than the bleach you buy in stores just stronger. I would get some Elemonator or other surfactant to add to your solution. Some people even use Gain laundry detergent. If you’re just a homeowner washing your own house that would probably be fine.

Be sure to rinse plants, landscaping, wood decks, and windows before applying solution. Let solution dwell for 5-10 minutes on house, don’t let it dry on the house so keep misting if need be, rinse with low pressure, and then rinse all plants and landscaping.


And excellent advice as usual from @marinegrunt

One big challenge @LGLDSR if you have a two story or large ranch house will be getting your mix/solution on the higher sections. Ladders or better equipment will be your options.

Keep in mind it will only draw from your mix/solution with the low rinse (usually black colored) tip.

Excellent, thank you! I will give it a try. If I should have need of Pool Shock (12.5%) I’ve more than enough left over from this past Summer.

Thanks again!


Thanks. It’s a single story range except for the area above the driveway which is a good 40’ up. Not looking forward to being 20’ up on a ladder to reach the top but it’s got to be done…



Get the tips linked below. Even a homeowner machine can come close to reaching the height you need to. They just take longer and aren’t efficient enough to use when running a business. You might have to pull out a step ladder and get a few feet off the ground but I bet for the most part you won’t have to use it.

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^ That’s pretty cool.
Does he need to have a certain minimum psi to push it that high?

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I don’t think it’s so much about psi although I’m sure you need some. Even cheap Craftsman washer are usually 2800-3400 psi. Although inefficient some people even soft wash with a 12v. I have a 7 gpm 100 psi 12v and that sucker will shoot 30’ when doing roofs. When we drop our nozzle size down to soft wash we’re basically dropping the psi of the pump into the low hundreds. Gpm is where it’s at although you need pressure for concrete work. There’s even guys who make a living using a small 2.2 gpm machine. How they do it is beyond me. I decided to use my old homeowner unit to wash my own house a few months back just to see and I lasted like 3 minutes. It was painfully slow. I guess it can be done but you have to think of it like this. A small gpm machine like that will take as least 3-4 times as long to wash a house. If a two story house normally takes 2 hours to wash you’re looking at at least 6 hours with a small homeowner machine. With a decent washer you can wash 3-4 houses a day where as with the smaller machine you’re basically stuck at one house a day because you don’t have time to finish another one. That’s a lot of money they’re losing out on. They could have a new machine paid off in like 2-3 days with the additional houses the could wash.

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Thanks Sir, I will order those!



Good information to know, thanks. The unit I have is 3.3GPM at 3400PSI.


3.3 gpm isn’t enough to wash houses professionally.

He’s just a homeowner washing his own house…