RO flow restrictor

[quazi]

So, what is the effect of no having a flow restirctor on your RO filter? I am not sure, but I believe I do not have one on my RO. I will look tonight and make sure. But I would like to understand the issue anyway.

Edited September 10, 2008 by quazi

[ReeferMan]

I believe it doesnt create enough back pressure for the water to filter correctly through the membrane meaning less waste water and more "bad" water getting through the membrane. But i could be completly wrong

[YBeNormal]

It either won't make product water at al or it will have an extremely high product to waste ratio. The flow restrictor may be in the form of an in-line canister/tube or it may be as simple as a small piece of plastic inserted somewhere in the waste water line.

 

What makes you think that you don't have a flow restrictor installed?

[quazi]

"What makes you think that you don't have a flow restrictor installed?"

 

I have never seen it and I never really looked for it. I saw a picture of one today, and I have never seen anything like it on my system. Your comment on what and where to look is helpful. I will look and see if I actually do have one tonight.

[WallyBackm]

if the waste water is flying out then you have no restrictor. It is important to get the proper restrictor based on the GPD rating of the membrane you have. I believe BRK sometimes carries them, otherwise marinedepot.com does.

[Coral Hind]

I had one were the flow restrictor was a metal piece screwed into the filter housing and the tubing insterted into it. The current one I have has a restrictor built into the flush valve.

[YBeNormal]

if the waste water is flying out then you have no restrictor.

 

Assuming your house have 30+ psi of water pressure and with the standard 4 to 1 or 5 to 1 waste to product ratio of a properly functioning RO/DI unit, the water will be flying out of the waste water line whether you have a flow restrictor or not.

 

The flow restrictor is always installed on the waste water line and its purpose is to apply a measured amount of back pressure on the RO membrane, forcing a percentage of the water to pass through the membrane while the rest of the water flows out to the drain and carries the rejected particles with it. If your RO unit has not flow restrictor, your unit will put out *very* little or no RO product water at all.

 

If the flow restrictor is not matched to the membrane, you will either:

- have a higher ratio of waste to product water

- or you will have a higher ratio of product to waste water but your membrane will become clogged with contaminants and wear out much faster than normal.

[Coral Hind]

Assuming your house have 30+ psi of water pressure and with the standard 4 to 1 or 5 to 1 waste to product ratio of a properly functioning RO/DI unit, the water will be flying out of the waste water line whether you have a flow restrictor or not.

 

It maybe just a difference of what someone considers "flying" but I have 60 PSI at my house and the water does not "fly" out of my waste line. It is a steady stream but it is not flying and that is 4 to 1 on a 75 GPD membrane. Now when I open the bypass or flush valve it flies. Just my observation, but the key would be to check your ratios of brine to filtered.

[YBeNormal]

OK, I'll buy that.

[Ne0eN]

Sometimes the restrictor is built-in with the bypass valve. Usually there is a number printed on the bypass/restrictor assembly indicating the flow in mL/min or gpd (I always wonder which one they use).

 

--Rob

Edited September 10, 2008 by Ne0eN

[quazi]

Thanks to all who replied. I solved the mystery. Apparently, there is a little restrictor pushed into the end of the waste tube where it connects to the filter housing. I have had this unit for 5 years, and never knew it was there! I guess I should buy a new one. I guess I will add that to the AirWaterIce group buy.

[YBeNormal]

It's good that you found it. Now please tell me why you think it needs to be replaced?

[quazi]

I have read numerous times to replace it when you replace your membrane. Since imy membrane has been replaced 3 times since purchase, I thought it was about time.

[YBeNormal]

I've never heard that but I guess it makes sense. Time for me to do some more research!

[quazi]

From SpectraPure:

 

Membranes must be matched with flow restrictors. Always change the flow restrictor when changing membrane size on your system...

 

http://www.spectrapure.com/St_replac_p3.htm

[lmeyer]

From SpectraPure:

 

Membranes must be matched with flow restrictors. Always change the flow restrictor when changing membrane size on your system...

 

http://www.spectrapure.com/St_replac_p3.htm

 

I don't think this means changing the flow restrictor every time you replace the membrane. I just ordered a new restrictor, but only because I am changing from a 24 GPD membrane to a 48 GPD membrane. The restrictor has to match the output of the membrane.

[cabrego]

I don't think this means changing the flow restrictor every time you replace the membrane. I just ordered a new restrictor, but only because I am changing from a 24 GPD membrane to a 48 GPD membrane. The restrictor has to match the output of the membrane.

 

 

Does the flow restricture effect the pressure within the RO unit I.e pressure gauge reading?

[YBeNormal]

I agree with the others on this one. The flow restrictor must be changed if you switch to a different size (in GPD) RO membrane, not if you replace with the same size & type membrane though.

 

Does the flow restricture effect the pressure within the RO unit I.e pressure gauge reading?

 

Yes and no. Let's say your house has 35 psi of water pressure. You will only see this reading when the water lines are closed and the lines are fully pressurized. Open a main faucet and the pressure reading on that line will drop to something much less than 35 psi. As you gradually close the faucet, the water pressure will begin to rise until the faucet is completely closed and the line is once again pressurized at 35 psi.

 

On your RO/DI unit, the flow restrictor will allow most of the water to pass but it will also maintain some back pressure and this reading will show on the pressure gauge. It will not increase your total water pressure though. Hope that makes sense...