Chorine or Oxidents Removal

I am currently using a slab on grade radiant hydronic system. Recently I discovered the problem with polybutylene pipe and how chlorine degrades the pipe. The radiant system is a closed loop system therefore I am not introducing new chlorine that often. Would some type of carbon filter help prolong the life of the pipe by removing the oxident if I used it on the water intake for refilling the boiler? Any suggesting on a good to very good filter for this application?

 

First a couple of questions.

What is the chlorine count in ppm? A simple chlorine test would indicate that count and a carbon filter could be suggested.

Let's say your chlorine is 0.5ppm. By having a closed loop system, once the chlorine is removed (converted to chlorides), it should no longer be the issue you are suggesting it to be.

Second. Is the water feed hot or cold? If it is hot, then I would not use a carbon filter but a KDF media filter (similar to shower filters) that work great at high temperatures and last sooo much longer than carbon of any type. The downside is, it is expensive. But it will be around for along time and it is a bacterialstatice media, meaning, it inhibits colonization of bacteria.

Placement of the filter is also important. What other waters would it be treating or dedicated to the heating loop only?

If you Cl count is extremely high, say, 5.0ppm than another approach may be necessay.

Andy Christensen, CWS-II

 

A properly designed closed-loop radiant system should not need to be refilled unless you perform a manual purge/blow-down.

Are you having to add water frequently ? - If so, you most probably have a leak in the system.

I presume you have a 1/2" makeup water feed with pressure regulator & RPZ as is common on well designed closed-loop radiant systems. Simply install/have your contractor install a cartridge-based filter on the influent-side of the makeup feed.

I most commonly specify DI/KDF cartridges to keep the makeup water as pure as reasonably possible.

 

No, I am not introducing new water to the system and apparently have no leaks yet. I am only concerned because I had a leak in the kitchen potable water system for no apparent reason and then found out about the polybutylene and chlorine issue. A pin hole had developed in a section of polybutylene pipe in the kitchen overhead. The inlet water is on the cold side. I performed a chlorine test on the water in the heating loop and it indicated a very low reading (close to or at 0) although the litmus was designed more for pool water. I tend to assume the chlorine has dissipated out of the system. The system has only been filled several times for maintenance reasons over the last 15 years. You mentioned the DI/KDF cartridges. I find KDF filters but not the DI/KDF cartridge. Can you give me a little more to go on? This filter would only be used for the closed loop hydronic heating system.

 

DI/KDF cartridges are custom built 50/50 mix of KDF-55C and standard mixed bed (anion/cation) deionization resin.

Our company builds them custom for each job, and I don't know of anyone who sells them as an off the shelf finished product, but you could probably have your local certified water specialist sell you some media and you could roll your own with a refillable cartridge shell. It's not hard to do.

 

Hey Greg, How's it going?

I hadn't considered a DI portion of the treatment. I guess it would determine the source water quality. If it were copper piping, would you still use DI as the pH may drop to low and cause corrosion?

Andy Christensen, CWS-II

 

Very good observation, Andy. Corrosion is a definite concern with DI and metallic piping. I like the DI water for makeup, not for filling the entire loop. I prefer filling with regular soft water and glycol, then using the DI/KDF for makeup, to keep the chemistry as close to "normal" as possible. We also use DI for condensate polishing on industrial steam boilers.

Are you coming to WQA/Aquatech in Vegas this year ?

 

Sounds like a very specialized filter for removing chlorine but what do I know and what does DI stand for? Do you suggest this approach for the average Joe blow and is this filter something your company, since I am not looking for a new adventure at the moment, is willing to make up for me without taking out a second? I’m not sure this other question is within your expertise, but do you have any practical advice on boiler water chemistry? I used to take, now and again a sample of water to the contractor who originally helped me with the hydronic heating system and he would supply me with a few chemicals to add. He has some time back went out of business. Maybe it's because of all the bolybutylene he buried in concrete. Anyway what is a good practical approach for a home owner to keep radiant floor heating water fit? There is a combination of copper, black iron and bolybutylene in the system with an oil fired boiler for the heat source.

 

DI is an abbreviation for DeIonization.

This type of resin is similar to traditional sodium/potassium & chloride type resins used for ion exchange.

DI resins are regenerated using hydrogen and hydroxyl ions (hydrochloric acid & caustic soda), so the exchanged ionic byproducts are essentially inert. That's why it's good to use the DI component of this filter to make sure that the new water coming into the loop is as clean as possible. The KDF-55 component neutralizes any free chlorine, thereby protecting the DI resin itself from chlorine oxidation and neutralizing any free chlorine to protect the heating system & it's components from oxidative damage.

This forum absolutely prohibits me from promoting anything my company does, so google my user name & contact me outside of this forum.

The key to water chemistry control in a residential hydronic heating system is to eliminate dissolved gases, keep the pH within a 'neutral' range, minimize dissolved hardness minerals, keep conductivity within 'normal' levels, and keep the water 'clear' (free of particulate).

Do you have any of your own water testing gear ?

Give us some background on your system...
Is your boiler cast or copper ?
Do you have cast/bronze/stainless pumps ?
Are you running all low temperature slab heat, or do you also have higher temperature baseboard heat zones ?
What is your water/glycol ratio ?
What kind of glycol are you using ?
Have you added any other chemicals to the loop (sequesterants, chelation agents, oxygen scavengers etc...) ?

 

Sorry for the delay, but I was pulling Polybutylene from my walls.

To answer your question about the system.

The boiler is a Vaillant cast iron boiler.

From the boiler is short run of black iron pipe that changes to copper then Polybutylene for the floor loops.

The return lines to the boiler are also black iron. Three cast iron Grundfos pumps are used in the system. One for the Vaillant DHW heat exchange tank,
one for the upstairs baseboard radiators and one for the 1800 ft of Polybutylene low temp floor loops.

The high temp upstairs baseboard radiators and lines are all copper after the cast iron pump.

So in short, I have cast iron, black iron, copper and Polybutylene. A few brass valves and dielectric unions are also used.

The only water testing equipment I have is litmus paper for PH and chlorine. I would not mind investing in other test equipment if I really knew what was important and knew what the chemicals were that I would need to balance the system after testing.

The only chemicals I have in the system now are “Davies Boiler-Kleen WBO” which is basically Sodium Hydroxide I believe.

The system is only filled with tape water which contains 1 PPM of chlorine. Does glycol have advantages?

How do you test for Oxygen Scavenger?

You mentioned several Items which could be tested. What would you say are the top three and what equipment would you need besides litmus paper? I would like to learn what maters in a residential environment and how to correct it.

I will email you about the DI filter.

 

This is the Hach kit that our field service technicians use when consulting on boiler applications:-

http://www.hach.com/hc/search.produc...TA5Sk1USQ==%7C

It's definitely overkill for a residential application though.

Hach sells some of the best testing equipment and chemical test in the industry & they'll sell direct to anyone.

I'd suggest their 5-in-1 test strips as a handy way of checking your chemistry.

http://www.hach.com/hc/search.produc...E1nPT1Ceg==%7C

That will give you the bulk of the critical data that you need without breaking the bank.

The most frequently used oxygen scavenger is anhydrous hydrazine, and you can buy tests for it from Hach.

Glycol is always mixed with the boiler water in a closed-loop configuration when snowmelt is used. Sometimes, the contractor will mix glycol into the loop to help prevent freezing of the piping inside the slab in the event of a boiler failure in cold weather even when there's no snowmelt. Glycol is less efficient at heat transfer than regular H2O, so unless freezing is an issue, it's (IMHO) not worth the maintenance hassle.

I've never heard of Boiler-Kleen WBO, but if it's just sodium hydroxide, it seems counter intuitive, since that will just raise the pH and induce massive precipitation of hardness minerals onto the hottest surfaces in the system.


You certainly have an interesting configuration. Have any of your pumps failed yet ?

Do your have any kind of microbubble resorber (spirovent, sparcovent etc...) or an air scoop ?

What did you replace your PolyB. with ?

 

Greg, I am going to follow your advice on acquiring what I need to take care of my system. This has been a very weak area for me and I will use your advice and recommendations. I wish to put an order list together from Hach. I will start with the 5 - in - one test strips. I looked at the oxygen scavenger test kit 2349500. Is this what you are recommending? So I don't have to keep ordering other items such as balancing chemicals, can you make suggestions for my order list? Is the anhydrous hydrazine available? It appears to be on the caustic side and I have yet to find a source.


As far as the air removal, I have four automatic vent valves located at strategic air accumulation points in the system. I do have a cast-iron air purge above the expansion tank, but I use the vent location for a temperature sensor for the computer system which controls the hydronic system and automated home. There were better places to mount the air purge devices.

As far as failures so far, I have had issues with dielectric unions. The dielectric material or seal fails. I did have an expansion tank develop a pin hole after about 10 years and replaced it. The new one went in about one month. After that I purged the water from the system and put new water in.

If your were interested I could show you things you have yet seen in a hydronic system and you might be better off for it. The home was built around the concept of energy efficiency, therefore the home is computer controlled in many ways to yield an efficient package. If we were to measure it in terms of energy use. I was running, until my last oil tank file (yikes!!) $39.00 average per month for DHW and heating for a 2700 sq ft home. Another story.

I replaced the Polybutylene with PEX due to the complexity of the runs. I hope it last longer then the Polybutylene did. The Polyb did have cracks near the ends with the most water flow (tees). The wave of the further my ####.

 

Lightfoot, I'd love to learn more about your green home !
Kudos on being environmentally aware.
I have a Tekmar 356 on my personal home boiler system crudely integrated to an HAI Omni Pro, and I'm always looking for new ideas

I wouldn't get the oxygen scavenger test kit yet, unless you're sure that your contractor has used hydrazine or a similar scavenger in your system. Did you figure out the Davies product that's in there ?

As a suggestion, replace any cast components that fail with stainless, brass or bronze - it significantly reduces your maintenance overhead on a residential system. I personally would replace the black pipe too, since it's just a rust nightmare.

Quite frankly, a full purge & flush would be in order if you notice any rust particulate in the loop water. - have you ever purged or flushed the loop ?

Good job with the PEX installation, I presume you used oxygen-barrier pipe ?

 

I'll answer and ask some more questions Sunday, but why would I want to use oxygen barrier PEX on a potable water system? It does not tie into my heating system at all.

 

My bad, I thought it was on your radiant.

 

The system has been purged after the pin holes developed in the second expansion tank. All the original oxygen scavenger chemicals and corrosion inhibitors were lost at that time. Since then I have notices the water in the system shows signs of darkening water which I would believe is rust. As I had mentioned, my heating contractor, at least the gentleman that provided me with testing and additives is now gone from the area and I do not have a replacement. I am under the believe I do need some type of corrosion inhibitor at least. Once I get a chlorine filter on the system and the proper chemicals to add I will flush the system. I am still uncertain as to where to acquire and what chemicals I need.

Some time in the future I plan to convert to an electric boiler because of the oil issue. At that time I will remove the black iron from the system if my polyb holds up.

 

Any good sources for anhydrous hydrazine for DIY home owners?