Boiler fill-soft or hard water

Mosherd1

I’m in the process of converting my house from forced hot air to hot water and am getting ready to pipe up my Taco boiler feed valve/back flow preventer. The system has a 50 gallon glass lined water heater with elements removed for a buffer tank. Our city water comes from a well drilled through limestone and has a hardness around 22 grains per gallon which puts it well into the “very hard” water category. I have a typical water softener that uses salt for ion exchange. Should the system be filled with hard or soft water?

JimP

My understanding is that the softened water will be more corrosive. I'd use the regular municipal water supply.

clammy

Have a de mineralized filter installed-on your water feed to the boiler for make up water . Have the installer add some purge valve and fill the system and use axiom purpro filter and install a de mineralized the boiler water then install the make up cartridge ( califee I believe na573 part #) . The make up water should be test for chlorides and total Dissolved solids . After water has test low add a inhibitor by a reputable company sentienal ,rhomar and adey all make fine hydronic inhibitors sentinel sells testing strips to ensure that you have enough in the system and weather or not the levels are low and more needs to be added it good insurance and also lowers corrosion over all in the system alongside w a bunch of other beneficially benefits in it use. On another note if a ecm circulator pump will be used install a magnetic dirt separator to protect it from iron oxide and magnite which will help protect and prolong your pumps life span . I like the adey magnetic dirt separator they work very well w magnetic particles which ecm pumps are not to keen on . peace and good luck clammy

clammy

As others may have stated run a un softened water line for your boiler feed and add the demineralizing filter . Soften water is not really recommended for boilerfeed water asother have eluded to again peace and good luck clammy

WMno57

I'm going to go against the grain (grains of hardness) and say softened water is better for your hydronic system.

Lot of threads on The Wall about this. Many of those threads have two misconceptions:

1. Household water softeners make Ultra Pure Water (UPW) which dissolves everything. (They don't)
https://en.wikipedia.org/wiki/Ultrapure_water

2. Household water softeners add chlorides to the water.

Water softeners do not make UPW. They perform an ion exchange and swap calcium, magnesium and iron for sodium. Most if not all of the chlorides get washed away in the brine rinse and purge cycle.

If you are really worried about the softener making the water too soft, make your own custom blend. Distilled water (its not UPW either) is a buck a gallon at Walmart.

I've owned rural homes with private wells and water softeners for 30 years. Mostly forced air, but the other appliances all lasted far longer than industry averages. My first home had a 35 year old circa 1970 water heater that had no leaks or problems. Second home has a circa 1990 water heater, still working.

My current 70 year old boiler is piped to fill from the water softener. Probably been that way for at least 20 years. I have a neighbor who knows much of the history. I'll ask him if he knows when they got a water softener.

Today's boilers are made out of tin foil. So it may be worth your while to purchase some water testing and if needed, make your own custom blend.

WMno57

If you pipe the feed valve to soft water, you can always add hard water to your system by flipping the bypass valve at the softener.

If you pipe the feed valve to hard water, that is all you will ever get.

hot_rod

what type of boiler? Most all boiler manufacturers state hardness less than 7 gpg or warranty is void. With 22 gpg, either deionize it, or haul in some good water to fill. Here is an example of Buderus water quality,I think this is for an aluminum block boiler.

WMno57

@hot_rod Thanks for posting that Buderus document.

It seems to contradict itself with the following two statements.

" Do not use water treated with salt bedding type exchangers (ion exchanger)"

" Maintain water hardness below 7 grains"

I would really like to know why water softened with an ion exchange water softener is supposedly bad for boilers. Specifically hot water, not steam. Is sodium worse than calcium, magnesium and iron? It has been my experience that softened water is much better for household water heaters.

Jamie Hall

Absolutely do not use water softened with ion exchange softeners. Yes, the hardness minerals are stripped out. But it is "ion exchange" -- and the exchanged cation is sodium. Some, but by no means all, of the chloride is rinsed -- but there is as much chloride left as there is sodium added.

So, basically, ion exchange softened water is dilute seawater. NOT what you want.

If your hardness is that high, I would use reverse osmosis treated water for the fill, and add a quality water treatment to control corrosion.

WMno57

Seawater has dissolved sodium chloride (NaCl or salt). Softened water contains sodium (Na), not sodium chloride (NaCl).

Seawater tastes salty. Softened water does not taste salty.

What is the difference between a household water heater, and a boiler in a hot water hydronic system? Millions of household water heaters are fed 100% softened water with no problems.

hot_rod

I feel at some point it is the lesser of two evils, exceptionally hard water in a boiler causes scaling issues day one.
So would 22 gpg cause more issues than softened??
IF you did soften down to say 3-5 gpg, you could add some hard water to dilute the softened.

The very best is water that has been stripped of both the + and - ions. RO, DI, distilling, rain water are examples of near pure water. Unfortunately rain does pick up some contaminants as if falls or if it touches the ground.
Once you purify water, strip it down to H2O the Ph will be a bit low, so buffer it up to 7's or better yet add a hydronic conditioner to the pure water.

Here is a good primer on hydronic water quality, showing and explaining the difference between softened and DI water process. And a good read from Rhomar

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_18_na.pdf

Jamie Hall

WMno57 said:

Seawater has dissolved sodium chloride (NaCl or salt). Softened water contains sodium (Na), not sodium chloride (NaCl).

Seawater tastes salty. Softened water does not taste salty.

What is the difference between a household water heater, and a boiler in a hot water hydronic system? Millions of household water heaters are fed 100% softened water with no problems.

Son, I'm afraid you need a chemistry lesson. Yes, sea water contains sodium ions. A lot of them. Softened water contains sodium ions. Not anywhere near as many, but -- interestingly -- exactly twice the concentration of them as the total of the calcium and magnesium ions which were removed. The anion in hard water is normally the carbonate ion (though in some hard waters it may also be sulfate). As I said, some of this is lost in the softening process, and replace with the chloride ion -- again, twice as much chloride as the total carbonate or sulfate removed.

If you are feeling very daring, you might try to obtain some metallic sodium and see what happens when you put it in water... wear safety goggles and gloves, and use tongs, as -- depending on the quantity you put in, the results may range from interesting to explosive.

Now... why doesn't softened water attack water heaters? Well, it does. Which is why water heaters, if they are to last any length of time at all, are glass lined or stainless steel, which softened water does not attack as fast. Most home heating systems are not glass lined, although some are made of varying grades of stainless steel, some of which resist attack pretty well.

And why doesn't softened water taste salty? There isn't enough salt. Sea water has about 35,000 ppm salt in it. Water at a hardness of 100 grains per gallon -- an obnoxious unit, by the way -- is about 1700 ppm, or 20 times less concentrated. And, in fact, some people can notice the saltiness.

WMno57

Pick your poison. Scale or Corrosion.

After reading the documents @hot_rod posted, It appears this is a pick your poison problem.

Hard water causes scale problems. Calcium and Magnesium are inversely soluble in water as temperature rises. When the water temperature goes up, the calcium and magnesium comes out of solution and coats everything with scale. Dissolved iron in the hard water will oxidize and become sludge.

Softened water has the calcium, magnesium, and iron replaced with sodium. Sodium is not inversely soluble, it stays in solution. But now there may or may not be another problem. Dissolved minerals cause the electrical conductivity of the water to rise. It's not clear to me if the conductivity of the softened water with sodium is any higher than than the conductivity of the hard water with calcium and magnesium. But too high electrical conductivity in water can lead to galvanic corrosion. Too low can lead to the LWCO not working. 10 to 30 PPM is the recommended range from Caleffi.

So which poison do you pick? If you have a heavy cast iron boiler, steel pipes, and cast iron radiators, you don't have a lot of dissimilar metals. Even if you do have corrosion, a few thousandths of an inch might not matter. Getting rid of the calcium, magnesium, and iron with a water softener has prevented a scale problem.

If you have a ModCon made with tin foil thick fancy alloys in a system with aluminum, copper, steel, and who knows what else, galvanic corrosion could cause an early boiler death.

@Jamie Hall I disagree that household water softeners add significant amounts of salt (NaCl) to softened water. I have said all along household water softeners add sodium (Na) to water. The chlorine from the NaCl combines with calcium adhered to the resin, becoming calcium chloride and is flushed in the brine and rinse cycles. If you have a source that says otherwise, would you post it please.

Mosherd1

Thank you for all the responses! @hot_rod no boiler yet. I bought this house a little over 4 years ago, did a complete gut job including all new mechanicals. I did all the work myself with help from friends too, the only thing contracted out was the spray foam insulation, and the connection/commissioning of the A/C. It took 3 years to “almost” complete-still working on some minor projects. I knew I wanted radiant heat, and roughed in radiant ceilings in part and floors in the other part. I’m an electrician by trade, worked for a general contractor during high school, and have an associate’s degree in heating and cooling, but I come from the land of natural gas/propane scorched air. The house is around 1200 sq feet with a ~35,000 btu heat loss, BUT here’s the kicker. Starting this spring we’re adding on a 4 car heated garage and a very large mother-in-law suite totaling approx ~3600 sq feet. So I’m not using a boiler at this point; I have a tankless feeding the buffer tank. I know the tankless is not the ideal heat source, but I don’t want to put a boiler in until I get the heat loss figured out for the addition and added to the original house loss. I’m going to use the tankless for a short term stop gap measure that is going to be repurposed in the addition.

Jamie Hall

What happens to the anions -- the carbonate, sulfate, and chloride ions -- in an ion exchange water softener is very complex, How much chloride winds up in the softened water depends very much on how the resin is regenerated. It might be very little, with most of the anions in the softened water remaining as carbonate or sulfate. It might be considerably more.

The bottom line, however, with regard to corrosion is this: as you note, the sodium ion does not precipitate out, unlike the calcium and magnesium ions. In a system with constant flushing, such as a water heater, the result is that the calcium and magnesium do tend to precipitate out -- to a certain extent -- as scale, and can result in a lot of scale, since they are constantly being replaced by the new water coming in.

However, in a hot water or steam boiler, if all is well, there is just one fill, and the calcium and magnesium will precipitate out just as before -- and then stop, since they have been depleted. If you use softened water, however, the sodium does not precipitate out, and the conductivity of the water remains high and corrosion will continue.

The nature of the anion -- chloride, carbonate, bicarbonate, sulfate, bisulfate -- is almost irrelevant.

AndrewB

(US Boiler) Burnham independence installation and operating guide specifically states the following:

Do not use softened water in steam boilers. Accelerated boiler corrosion will result. Tie in fresh water
supply to the boiler upstream of a water softener.

hot_rod

On a small residential system you will probably have around 30 gallons of total fluid capacity. You might just get a 30 or 50 gallon plastic barrel and buy some DI water. See if you have a water treatment supplier near you, many have DI towers and will fill your container. Automatic car washes mostly use RO for the final rinse for a spot free dry They usually store 1000 gallons in a plastic tank, see if they will fill your barrel.
$2.98 for 2.5 gallons of Ozarka Spring Water at my WalMart Some WalMarts have a water purifier, you fill your own jugs with. Before we got our well sorted out we used to fill 5 gallon containers for drinking and cooking, it was years ago, I think a buck a gallon.
If you use RO or DI I'd squirt a can of Rhomar or Fernox conditioner into buffer the ph, etc.

sunlight33

Does anyone know if the Fernox aerosol can adapter is compatible with garden hose thread? The product is made in UK so I am worried if they have different thread size there.

hot_rod

make sure the connection is tight, the cans empty quickly.