Pure water for pressure washing

Hello fellow window cleaners!
A customer has asked me if I can come up with a solution for his problem.
He ( the customer ) is having his cars washed /cleaned /pressure washed twice a week or so in front of his garage with glass garage doors. They don’t dry the cars properly ( don’t know why) and end up with spots from minerals on cars and spots on glass garage doors that I remove chemically every time I am there.
I know they are using an electric pressure washer 2,5 gpm , total 2h per week, I would say…
Is there a way to get a system before pressure washer so that they clean with pure water and don’t leave spots?
Another client of mine had a big system built in the basement of his house so that ALL cold water in his house is RO, perhaps that would be an option? They are not trying to come up with a cheap solution, but an effective and long lasting one.

  1. RO to large tank, then a belt driven pressure washer
  2. RO to small or large tank, then electric sprayer to rinse cars after electric pressure washer
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Maybe have his cars washed properly away from the glass garage door?


Umm, stupid. Get a better car cleaning company. So stupid.

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Amazing isn’t it :rofl::rofl:. The last guy was half your price .

What’s the TDS of the water supply? If it’s low enough, it might make sense to just run one or two DI tanks before the pressure washer.

If your water is on the harder side, then RO to a buffer tank would be the way to go.

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There is no way a di tank is cleaning water with 4gpm running through it

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I think either way he should be running whatever he uses to filter the water before the buffer tank
For my WFP I run my DI tanks after the buffer tanks.

Challenge accepted.

For a bit of an explanation: DI tanks generally don’t have much flow restriction to speak of.

It’s possible that some tank manufacturers add an artificial flow restrictor for the sake of ‘more thorough filtering’ or something. But neither of my tanks appear to have that sort of restriction.

I don’t have especially awesome water pressure at my house. I might get another .5 gpm out of my hose without the DI tanks there. So the tanks are probably the equivalent of adding another 50’-75’ of garden hose.

That said, I feel it’s always better to pull from a buffer tank than from your filtration system, just in case something clogs up the works.

My recommendation (for a soft water area and a gear/belt drive machine):

Water supply → Sediment filter → dual half cube DI tanks → small buffer tank with float valve → pressure washer

But if it’s a direct drive machine with 4gpm or less flow, and you’ve done a bucket test to check the flow rate out of your DI tanks is 4.5+ gpm:

Water supply → Sediment filter → dual half cube DI tanks → pressure washer

Make sure and take frequent readings after each DI tank. Change the resin in the first tank when its TDS reaches about 50% or more of the tap TDS. Then rotate that fresh tank to the front of the line.

Allowing the TDS to get too high in the first tank can cause a leaching effect when the resin over-saturates with dissolved solids, and you can actually end up fouling your second tank faster.

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Like the way you joined those two tanks together.

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Finally got around to doin this today. After leaking everywhere for months and months
You just don’t put one and one together till you see it sometimes.

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Bada bing bada bom !


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Glad you found my setup helpful!

For a moment, when you mentioned ‘putting the two tanks together’, I thought you were talking about this:

The two water tanks on my rig are plumbed together so that I can pull from either the buffer, pure water, or both simultaneously. (It’s backfired on more than one occasion, unfortunately. I forgot to switch the valves back to this standard configuration, and proceeded to empty my pure water tank just washing screens or whatever before getting to clean any windows :man_facepalming: :joy:)

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Is there some sort of spray gun that fits on the little waterfed hose? I’d like to rig my DI tank so someone can rinse off the windows after softwashing.

With my set up I just use my buffer tank. The pump pulls form the buffer , and then it runs through the DI tank . No need for a separate tank for Pure water.
Works out great that way. I have a 200 gallon buffer.

The little green hose in the picture goes to my ds injector 3-way poly valve, for rinsing it out at the end of the day.

I can pull pure water from the tank with the pressure washer, and rinse with that if needed.

I still need to install a 3-way valve on the bypass line. Right now how it’s setup, bypass will just fill back into the regular buffer tank. So I gotta stay on the trigger if I want to use the purified water efficiently.

I really gotta shoot a video soon running through my whole rig.