Stainless Steel vs RODI

[ithk21620]

Not sure if this is within your specialty but I want to install a solenoid valve on my 1/4" RODI line that feeds my top off float valve. My concern with this idea is that the body of the solenoid valve is plastic but the plunger is not. The plunger is stainless steel but with the water being stripped clean of elements it will strip some from the plunger over time.

Is this small amount of elements going to affect my tank?

I could obviously avoid the whole thing with a actuated PVC ball valve but then I am looking at $300 vs the $30 for the apex one or even cheaper for a generic one.

 

[Randy Holmes-Farley]

What grade of stainless steel?

Some grades are fine, even in a reef tank itself.

 

[revhtree]

What grade of stainless steel?

Some grades are fine, even in a reef tank itself.

I did not know that!

 

[Randy Holmes-Farley]

The arms on my float switches made of 316 stainless steel were in my reef tank for 20 years. When I removed them, they had a coating of calcium carbonate on them, but were otherwise fine.

 

[revhtree]

The arms on my float switches made of 316 stainless steel were in my reef tank for 20 years. When I removed them, they had a coating of calcium carbonate on them, but were otherwise fine.

WOW! LOL!

 

[ithk21620]

What grade of stainless steel?

Some grades are fine, even in a reef tank itself.

I am assuming they are 304 or lower but I have asked the different companies what their valves are made of to verify. I will let everyone know what I find out.

I was always taught that even SS was not good with DI water because it will stop some ions from the metal regardless. I asked the question because I wasn't sure if the small amount that would be stripped would actually cause an issue in a reef tank.

I know at work we can not use any metal, SS included, on the DI water lines for the food lab because of this.

 

[ithk21620]

What grade of stainless steel?

Some grades are fine, even in a reef tank itself.

So this is the information I received back from some of the popular solenoid valves and brands I have seen people use:

Avast Marine 12VDC solenoid valve (http://www.avastmarine.com/products/solenoid-valve-12v)
304 Stainless Steel Stem and Spring

Apex SV-1 (https://www.neptunesystems.com/fmm-accessories/)
"Support does not have any specifics on the material used in the the solenoid. It is some type of metal not suitable for saltwater at this time, designed to be used in a ATO situation" I find this comical...

WIC Valves 2PCK (http://www.wicvalve.com/1-4-Inch-Plastic-Electric-Fast-Response-Water-Solenoid-Valve-2PCK-1-4-G.htm)
304 Stainless Steel Stem and Spring

While looking at the WIC valve specs I did find some solenoid diaphragm valves at a reasonable price so I think I am going to go that route since there is no contact with any metal. Here is what I am thinking of using. http://www.wicvalve.com/1-2-Inch-Pl...ir-Gas-Water-Solenoid-Valve-NC-2PCG-1-2-D.htm

 

[holdthecoffee]

Hi ithk21620,

I know this is an old thread, but how did your solenoid valves workout for you? Which one did you specifically buy? I think the link has changed.

I am also in the market looking for solenoid valves that would work with my RODI system. I was thinking of buying some from autotopoff.com (http://autotopoff.com/Solenoids/index.html) since I have used them in the past, they are very affordable, reliable and they worked great. But after reading your comment about the plunger being stainless steel and can leach metal into my tank, I'm not so sure anymore.

 

[Randy Holmes-Farley]

Hi ithk21620,

I know this is an old thread, but how did your solenoid valves workout for you? Which one did you specifically buy? I think the link has changed.

I am also in the market looking for solenoid valves that would work with my RODI system. I was thinking of buying some from autotopoff.com (http://autotopoff.com/Solenoids/index.html) since I have used them in the past, they are very affordable, reliable and they worked great. But after reading your comment about the plunger being stainless steel and can leach metal into my tank, I'm not so sure anymore.

where in the system do you intend to use it?

 

[holdthecoffee]

I was planning on having some one before the RO membrane, one between the RO and DI, and two after the DI.

In order to do my ATO:
1) Once a day, I will have a timer open a solenoid before my RO membrane to wash out TDS creep.
2) One minute later, the solenoid between the RO and DI will open allowing water to fill up a pressurized water tank. This tank is located before my DI. The timer will shut off both solenoids after 10 minutes (I have a 180gpd RO membrane).
3) Whenever my ATO activates, it will open the two solenoids after my DI which will allow the water from the pressurized tank to go through my DI resin and top off my tank.

Haven't set this up yet, but this was my plan plus some redundancy to prevent flooding like a mechanical float valve and flo-locks. I didn't plan on using an ASO with this since my first solenoid should shut off water to the system, but if anyone has advice, please let me know.

 

[Randy Holmes-Farley]

I would just put solenoids before the RO membrane to avoid metal dissolution. Any cheap solenoid will work for that.

I have also found that some solenoids need pressure to work properly, and may not always actuate properly, say, after the RO membrane. I used solenoids for a cooling system, and found that if I reduced the flow/pressure too much, the solenoids malfunctioned.

 

[holdthecoffee]

Hmmm the problem with only having solenoids before the RO membrane is TDS creep.

I think I'll move the two solenoids controlled by my ATO to be between my pressurized tank and DI, instead of placing them after my DI. That way if it leaches anything, the DI resin will pick it up.

I'll have to monitor about that pressure issue you mentioned with solenoids not working well with low pressure.

 

[Randy Holmes-Farley]

Hmmm the problem with only having solenoids before the RO membrane is TDS creep.

I think I'll move the two solenoids controlled by my ATO to be between my pressurized tank and DI, instead of placing them after my DI. That way if it leaches anything, the DI resin will pick it up.

I'll have to monitor about that pressure issue you mentioned with solenoids not working well with low pressure.

TDS creep is a reasonable concern, but likely ends up costing less in more frequent DI replacement than solenoids will cost.

I think the creep of ions along a stretch of tubing is very limited. IMO, it is mostly across the membrane and then mostly stops once the two sides of the membrane reach the same TDS. Ongoing diffusion of ions along the tubing to the DI is going to be very slow. Diffusion is a remarkably slow process.

 

[holdthecoffee]

That's a pretty valid point about cost of DI vs solenoid. I guess I'll check both methods and see which method I like more. Thanks for your suggestions.

 

[K7BMG]

I would not go overboard with controls.
More mechanical controls the more failures and problems you will have.
Just the nature of the beast.
In mybwork I fight this all the time with engineering personnel.
Inask them are you implementing all this to impress everyone, or are you looking at the customer needs and what it will they will have to deal with.

More than not the kis system is the best system.
Kiss= keep it simple

 

[ithk21620]

Hi ithk21620,

I know this is an old thread, but how did your solenoid valves workout for you? Which one did you specifically buy? I think the link has changed.

I am also in the market looking for solenoid valves that would work with my RODI system. I was thinking of buying some from autotopoff.com (http://autotopoff.com/Solenoids/index.html) since I have used them in the past, they are very affordable, reliable and they worked great. But after reading your comment about the plunger being stainless steel and can leach metal into my tank, I'm not so sure anymore.

Sorry for the late response, looks like Randy answered most of your questions. I have yet to install a valve between my RO holding tank to my top off, just have the hand valve still which works fine but eventually I will replace it lol.

As for the valve feeding my RO unit I ended up just going with a cheap sprinkler system valve. I was going to go with a small solenoid valve but figured feeding the RO unit with full line pressure and volume would be better. Plus the parts to rebuild them are easily obtained from the local hardware store. I figured if it was built to turn sprinklers on every day or so over the course of the summer it would be fine for the amount I turn the RO on. It has been working great so far, plus has a manual way of turning it on without power if I wanted. My RO system has an auto flush valve so I didn't feel the need to add any valving after it since the TDS creep is tiny and my three stages of DI will clean it up without issue.