DIY Softwash Metering System


Thanks! Yes, those Plastomatic diaphragm check valves are what I would recommend using, and what I’d opt for if given the option. Though it’s probably only really needed on the SH supply, the OCD in me would want them on the water and soap as well.

I don’t have a link to where I’m getting the hastelloy check valves because I’m getting them through supplier for my day job company and I’m getting a pretty big discount through them. However, they are made by a company called Specialty Manufacturing Co and they have a website and it’s pretty easy to look through it and configure the check valves you want. They don’t make larger than 3/4", and they don’t offer it in PVC, which is less than ideal as well. Polypro doesn’t hold up as well in sunlight as PVC, so that could be an issue with a setup not covered or shaded. The diaphragm check valves are PVC. They may discolor slightly over time from sunlight/UV exposure, but it doesn’t degrade at all or lose any of it’s great properties.

I do think that 1/2" on proportioner is too small. But it’s the easy and cheap way to make a setup, and obviously it works well. It’s just not really what it should be. 3/4" would be great, and 1" might be best, though I’m not sure if there is any performance difference in 1" over 3/4". I’m still working on getting details between those. The issues are the 3/4" metering valves are harder to get, but 1" valves and components cost quite a bit more than 3/4".

I just placed an order for all the components to build the first setup, using 1/2" GF metering valves and 1/2" hastelloy spring check valves. Parts should arrive in 3 weeks (fittings in 1 day, check valves have 3 week lead time). Once it all arrives and is built, I’ll put up photos and everything for people to see and get feedback.

I’ll be ordering parts in a few weeks to build a 3/4" metering valve setup as well, but those valve have an 8 week lead time, so I’m waiting for the supplier to stock them again before placing an order.


Alright this a total newbie question but not something I’ve seen covered in this post.

With this setup how much, let’s say SH, will you draw per minute? Or another way to ask it is how large of a storage container would you need to run this for thirty minutes at a given target ratio using the 12 v applicator. Aren’t the gpm of these systems pretty high?


Depends on how strong your mix is. The two most common 12V’s are 5.5 GPM and 7 GPM. Boosters are there, and a little more. So if you wanted to spray straight bleach, just do the math. If you only wanted a 3-5% mix, say for a roof, then you use those numbers.

So just using numbers and no variants… straight 12.5 with a 5 GPM, a 55 gallon drum would last 11 minutes. Mixed 50/50 would last 22 minutes. Etc.

It’s essentially the same as if you batch mixed it, it’s just that you are mixing it on the fly. Benefit is that you can vary it as you go, which saves chemical. Also, you dont have to stop and make a new batch when you drain the first mix tank.


And remember that even though i said 55 gallons of 50/50 would go in 22 minutes, thats with the trigger pulled constantly… which isn’t how you normally apply a roof mix.

It will take the same amount of time to go through 55 gallons with a metering system, as it would a batch mixed drum.


Would also depend on what your actual GPM output is. Not sure if anyone has put flow meters on the outlet side of their sifteash susten or not, but using 1/2" valves, and especially with metering one or more of them both acknowledged from full open would likely reduce output.


Yes, you’re right. Lots of variables that affect the outcome.

Mostly i was just trying to get across that batch mixing and metering are exactly the same, in terms of how much chemical they use during application.

Metering allows you to vary the concentration on the fly, however, which saves chemical. Also you can delete a mix tank from your setup, and carry more bleach in its place if you want… which will allow you to go longer before needing a bleach fill up. Super efficient way to do things.


Sounds good, Keep us all posted !


Just got off the phone from a long conversation with Rex from Pressure Washer Products regarding various metering system design approaches. I learned several things from him. He said that proportioners put a lot of stress on 12V diaphragm pumps and AOD pumps because it restricts the flow and causes the diaphragm to have to “suck” harder, which in a short amount of time, can rip or tear the diaphragm right open. He also proposed that the idea of a 3rd incoming line (soap supply line) is unnecessary and to keep flow levels at the highest possible rate, soap should be mixed into the SH at the appropriate ratios. This would put less stress on the diaphragm. Makes sense to me.

So just looking for feedback on if you guys think a 2 line system would work well if you had the option, or if you guys would still prefer having a 3 line system to meter from? Just curious on preferences.

It sounds like they sell a lot of pumps and get a lot of issues from guys putting proportioners on them and then damaging the pumps not long after. Must be pretty frustrating to deal with.


I like the idea of two lines. This would bring the overall cost down, as well as extend pump life. The time it takes to add soap to SH is negligible. If your pump goes down, then you are spending much more time and money for repair/replacement. By only having 2 lines, you reduce your chance of pump failure by 1/3?? Is that accurate or am I justifying my opinion with crappy math? Lol


I think the math is wrong lol, but the idea seems correct. Haha.


To me, I think this kind of defeats the purpose of the metering system. If you mix soap into your SH tank, then what happens when you want to use more/less/no soap? Or a different soap? Then you’re back to portioning out SH to add soap to it… which is batch mixing.


I agree, I told him the same thing. He just looks at it differently though. He was saying that his customers don’t vary their mixes really, just maybe 2 different ratios, and always the same soap, 8oz per 100 gallons of SH. He also said if his customers are out washing and 1 part of the roof is really bad and needs 30%, but the other parts are okay and only need 3%, they’ll still spray 30% on the whole thing so they don’t have to have different mixes, and if they had a 2 line metering system, they’d spray the stronger ratio on everything, even what didn’t need a strong mix.

I understand that this is not as cost effective because you use a lot more chemical than you need to, but he said they have over 6000 customers and most of his softwashing guys do it that way.

Not saying its right or wrong, just his recommendation from his experience.


@jzbreeland I respect that guys opinion greatly but i think we should stick with making the highest quality / optimally flowing (3/4 - 1inch setup) 3 way metering system we can. Iff he thinks the pumps are the issue in the long run, maybe we should look into booster pumps? or just other pump alternatives instead of abandoning the idea of the 3 way WATER/SH/SOAP setup. just my 2cents.

    I completely agree... I think the 3 way would be the most popular, but having a plan with a 2 way would also appeal to a lot of people. I do not change my soap or ratio of soap to SH much at all... the 2 way would conceivably cost less and benefit me the most for my setup.
   The 3 way has proven Itself already, and the initial planning and building should be done to maximize that setup.


You’re message shows up as hard to read for some reason. Weird.

But I understand. If a person did want to only use an SH an water line setup, they could always just close the third soap supply line metering valve and run it as a 2 line system. The cost savings between a 2 line and 3 line setup wouldn’t be very significant anyway. Maybe $100 or less, and in the scheme of the cost of the setup as a whole, it’s not a huge difference.

I have someone I’ve been talking with privately who has agreed to purchase the first “prototype” so to speak as a test run, and I’ll likely order the parts for him this week. Once he and I figure out exactly what he wants, I’ll get the parts and build it to send to him. Once that’s all set, I’ll post up photos for everyone to see and get feedback, and he should be able to give feedback as well on how it works for him. He is washing with a booster pump, not 12V. So hopefully soon. :slight_smile:


I really don’t know why my post shows up like that?.. it is very strange.
Great post… that makes a lot of sense as to why you could just build one model with the 3 way. Your knowledge in this thread is greatly appreciated, and I am definitely looking forward to the prototype and testing outcomes.


That’s the reason I suggested going to bigger lines. That will help alleviate that problem. The Proportioner as it’s designed now is for 5.5gpm flow.

I wouldn’t be interested at all w/o the soap line.


Thanks @Racer for your input. I’m glad to know you think the soap line is necessary. I feel the same way, but I guess just not everyone has the same opinion. I know you do a lot of softwashing though, so I really value what you say.


Do you think it would matter if i ran 2 different types of check valves in the setup?

i would use this 3/4 inch for SH

This 3/4 for water

and this 1/2 for soap

and just before anyone asks why. It would be for cost savings. the diaphram check valves are very expensive… i understand spending the money on that specifically for the SH. But if just water and soap are flowing through the other check valves with hallestoy springs, it should be fine right?


I wouldn’t suggest going with different types of check valves between SH and water because they aren’t going to flow the same and your mix ratios aren’t going to be as accurate.

Also, you don’t need CPVC, and it’s a lot more expensive.

Also, you don’t want EPDM seals. Viton holds up better against SH. The water line might see some SH on the downstream side of the check valve from back pressure.

Also, where are you going to get 3/4" metering valves? I’ve only found one place, they aren’t in the US, and their 3/4" is 8 weeks backordered because it’s an uncommon size for them. If you are going to run 3/4" check valves with 1/2" metering valves, there is no point.