Hydraulic expert needed

markba633csi

markba633csi

Mark Silva
H-M Supporter Gold Member
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Apr 30, 2015
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I know this is a bit off topic:
We have a water filter in line A and an adjustable valve in line B, then we T them together. (both originate from the same common line)
We adjust the valve to give 50/50 flow from A and B.
As the filter clogs, what would be the minimum amount of hardware to maintain the 50/50 ratio?
Would it require a regulator on both A and B lines before the T? Or is there a special type of regulator for this?
Thanks
Mark
 
Have to think it over for a bit, But I'm thinking you will need at least a pressure regulator to maintain a constant pressure. But that would make that side a lower pressure then the other side, so you may need 2 regulators to give each side the same pressure.

I think the first question, is how much would the pressure drop as the filter builds up before you would change it. I have had whole house filters get quite dirty looking, but never noticed any change in pressure or flow after changing them. I'm thinking you may be worrying about an issue that will not likely be an issue.

The next question, is why do you only want to filter half the water going to a faucet?
 
I think what you need is a flow divider. Somewhat common in hydraulic systems, but I have never seen one for a water system.

Google Flow Divider
 
It's a dedicated line for a coffee machine. My water is pretty good municipal water but the hardness is about twice the recommended amount, which will scale the boiler in a few months time. I wanted to use a simple cation softener cartridge but blend with untreated water to maintain the taste, and then only have to descale about once a year. It could be that the flow won't change appreciably before the cartridge is exhausted so maybe just a simple valve would suffice. Time to experiment! (I love having an excuse to experiment) ;) Off to buy a water hardness test kit!
 
JimDawson said:
I think what you need is a flow divider. Somewhat common in hydraulic systems, but I have never seen one for a water system.

Google Flow Divider
Click to expand...
I have heard of them for one input, into two outputs, but do they make them for two inputs, into one output?


markba633csi said:
It's a dedicated line for a coffee machine. My water is pretty good municipal water but the hardness is about twice the recommended amount, which will scale the boiler in a few months time. I wanted to use a simple cation softener cartridge but blend with untreated water to maintain the taste, and then only have to descale about once a year. It could be that the flow won't change appreciably before the cartridge is exhausted so maybe just a simple valve would suffice. Time to experiment! (I love having an excuse to experiment) ;) Off to buy a water hardness test kit!
Click to expand...
Interesting idea. For that little use (I'm a big coffee drinker, so don't take that wrong, just comparing to other uses in the house), I would not do any thing fancy. likely just the valves, and probably add two pressure gauges, so you could check every so often to see if the flow is being impeded. Just remember you would have to check the gauges when the pot is being filled, or another valve on the output line is open. With no flow, the pressures would be the same.
 
Superburban said:
With no flow, the pressures would be the same.
Click to expand...
Yup. The first thing we learned in Hyd class is- "Pumps make FLOW. RESTRICTIONS to the flow make PRESSURE. As I see it, as the restriction in the filter increases, the restriction in the other line must also, to maintain equal flow. Identical pressure regulators, one the downstream side of the filter, and the other on line B would result in equal flow, I think. Then again, my thinking is occasionally restricted, and flow is therefore reduced.:cautious:. And I don't even want to talk about "pressure drop":big grin:
 
I believe it would actually take 3 regulators to do a proper job of it, the third one after the blending Tee. But I think it's probably way overkill for this.
I'll try some tests with various blend ratios and do some hardness testing. Need a good repeatable valve like a Deltrol Easy-Read with the micrometer adjustment- Stainless steel of course $$
 
We sell filters if you're in the market ! SS too ! You could probably run it a lifetime with no pressure or flow differential . :big grin: Google LMO filters . Or , I may be able to get one on the cheap , if they let me .
 
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It sounds like you could use a pressure-balanced mixing valve, commonly used for showers. That would be a fairly inexpensive, readily available solution. Note, some shower mixing valves are thermostatic balanced and would not work in you application.
 
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