Soft vs. hard water

[damon_sisk]

I'm installing the plumbing for an EKO 40. I insulated and buried two 500 gallon propane tanks for thermal storage last winter.
Should I go to the effort of revitalizing my old water softener (or buying a new one) just to fill the 1000 gallons with soft water?
My water hardness is 17 ppm CaCO3 (I think that's what the Culligan man measured; in any case, he said we have quite hard water.)
I separated my boiler loop from my thermal storage tank loop with a brazed plate heat exchanger. My concern with the hard water is calcium deposits on the inside surfaces of the brazed plate heat exchanger and on the inside of the tubes in my water to air heat exchanger (for forced air/duct work system).
My concern with soft water is that it seems like the salty water might corrode things worse (just guessing.)

Any advice/experience?

 

[stee6043]

I have a water softener and opted to use non-softened water to fill my system. I spoke with a couple of folks that seemed to suggest the salt in the soft water may actually be abrassive over time in the system (not necessarily corrosive).

You're planning to treat the water either way, correct? I'd go hard water and I would buy a $40 in-line filter (the whole house kind) to filter the water while you fill. That's just my opinion.

Silly question - but why are you using a plate HX if you have propane tanks for storage? One of the big reasons to go with propane tanks for storage is so you can avoid the HX....

 

[damon_sisk]

The propane tanks are insulated and buried below the frost line. I plumbed them into the house through the basement wall. My boiler is in my attached garage, that way I don't have to carry wood through the house. I didn't want to build a shed for the boiler, and I don't want to pay for enough antifreeze to protect the 1000 gallons of storage.
I bought a high temperature filter & filter housing so that I can prevent any junk from getting into the plate HX.
I do plan to treat the storage water such as 'Solution 101' (http://www.cozyheat.net/101.html) but probably not for a month or so after filling the storage and boiler.
What would you recommend that I treat for?

 

[in hot water]

There really should not be salt in the softened water if the softener is working properly. A softener is an ion exchange device, salt is exchanged for the calcium then flushed down the drain.

Better yet is DI or DM water" de-mineralized' water is made with a single pass filtration, no salt. Culligan and others rent these systems and bring them to the jobsite for large installations. For small jobs I would haul DI water from a local source in a 50 gallon plastic drum. Typical residential hydronics hold 30- 50 gallons.

DI water is critical for blending glycol antifreezes, or you ruin the hardness package in the glycol inhibitor.

Some installers blend the DI water with the water at the site, split the difference.

hr

 

[damon_sisk]

That's true, there would be no grainular salt in the softened water. I understand that the salt dissociates into ions that are exchanged for the calcium. But the sodium and chloride ions being in the water concerned me, since that would be a bit like ocean water (of course, not as salty.) Thanks for the tip about using DI water. I'll check with Culligan to see what it would cost to rent a DI for the fill.

 

[damon_sisk]

I wasn't thinking properly in my last post. I would only need DI water for the boiler (~30 gallons minus antifreeze) since I don't plan to put glycol and therefore inhibiters in the 1000 gallon storage. Are there other advantages to DI water for the 1000 gallons storage system?

 

[Corey]

If he really said 17ppm, that is about 1 grain per gallon (ppm / 17.1 = gpg) which is considered soft water. If he said it is 17 grains per gallon, that would be about 290 ppm which is pretty hard water.

If you're really at 17ppm, I wouldn't worry about it too much. At 17 grains / 290ppm - that is pretty hard water. Probably still wouldn't cause too much problem as you aren't putting a bunch of water 'through' the system. ie this isn't a true steam boiler with lots of feed water - more of a water heater where you have the initial fill and possibly a top-off now and then. Though it might be good to look at other water parameters, too - total dissolved solids (TDS), alkalinity, pH, etc and make sure they are within agreeable limits.

 

[damon_sisk]

You are right Corey. In looking through the various hardness measuring units, he must have said 17 grains per gallon. I know I have hard water; there are deposits on my shower head. If I clean them off, they reappear in a few months.

 

[in hot water]

the small tight spaces are the place the hard water deposits will nest, like the plate HX. The temperature has a bit to do with how the hardness fall from solution and settles out. The higher the temperatures the more the minerals fall from the water. This can be seen on electric water heater elements. One day after they are installed in hard water conditions they are coated with "hardness. Years later they can have 1/4" or more of deposits adhered to them. eventually an element fails when it cannot exchange the heat to the water.


If you have a softener, I run the water through that, the lesser of two evils. Google around and you will find that a few thousands of sediment on HX surfaces really drive down the HX performance. Depending on your sizing, maybe it will not be and issue. And if it coats the HX from day one, you may never know the HX penalty.

If you do fill it through the softener does yours backwash on demand, after a certain amount flow through? Or is it a clock timer type. With a clock timer they backwash based on time not gallons run. The demand regeneration units I like better, they backwash after the amount of gallons flow.

If you have a 17,000 softener, it will treat 1000 gallons at 17 grains before backwashing. In my plumbing days we installed 24 or 32,000 demand regeneration sizes for most residential applications. Too small and they backwash every few days, they really need to be sized to your water hardness and water use.

hr

 

[reguy]

How about collecting rainwater off the roof?

 

[damon_sisk]

The rainwater idea will take too long, since I'm trying to operate the system this winter.

HR: Hard water deposits adding heat transfer resistance in the plate HX is the main reason I'm considering soft water for the 1000 gallon storage. But I'm not sure if the calcium from 1000 gallons will be significant. Ideally the system is closed (assuming no leaks ), so it is not like the water heater where fresh utility water continually drops deposits on the heating elements.
Thank you for the info about water softeners. Mine is an old Culligan 500C 'water conditioner'. The DIYer in me wants to upgrade its clock controls to demand based and replace the resin rather than spend $500 for a new softener. Is there a correlation between resin volume and the size (17,000 etc.) of the softener? I'm trying to figure out if mine would be undersized even if functional.

 

[heaterman]

FWIW........Softened water is actually a bit more corrosive than unsoftened water from what I have been told. Something to do with the ion exchange in a softener. Maybe HR knows......... At any rate. When we do a closed system with large capacity we call up a local water treatment company, have them deliver jugs or drums to the job site and pump it in after first flushing the system out. The inhibitors and/or antifreeze will last far longer and you'll likely need less of the chemical additive. For semi open systems like a Garn, the recommendation is no more than half and half hard/soft. Might be worth a call to the manufacturer of your boiler to see what they recommend. At any rate, I would suggest that once you get things in operation, get in touch with a reputable water testing company that specialized or has experience with boilers and have them do a work up on your system fluid. It'll pay off in the long run and the testing is not that expensive. Far, far less money than the two days of labor we just spent draining and power washing the inside of a couple of very abused Garns.

 

[brad068]

FWIW........Softened water is actually a bit more corrosive than unsoftened water from what I have been told. Something to do with the ion exchange in a softener. Maybe HR knows......... At any rate. When we do a closed system with large capacity we call up a local water treatment company, have them deliver jugs or drums to the job site and pump it in after first flushing the system out. The inhibitors and/or antifreeze will last far longer and you'll likely need less of the chemical additive. For semi open systems like a Garn, the recommendation is no more than half and half hard/soft. Might be worth a call to the manufacturer of your boiler to see what they recommend. At any rate, I would suggest that once you get things in operation, get in touch with a reputable water testing company that specialized or has experience with boilers and have them do a work up on your system fluid. It'll pay off in the long run and the testing is not that expensive. Far, far less money than the two days of labor we just spent draining and power washing the inside of a couple of very abused Garns.

Heaterman, you ever went back and tested pH and nitrates on garns. I tested mine and the neighbors and was surprised to fine that on mine the fill was 5.71pH and nitrates 6ppm, and after a year the pH was 8.96 with 1.2 ppm NO3. No chemicals and as you can see, acidic fill. Neighbors was 6.51pH fill and 8.9 NO3, year later 9.24pH and 3 NO3. I was surprised that the pH rose that much without any chemical additives.

When we cleaned and refilled this year we both had some "barnacles" on the steel pipes but they can right off with wash water.

 

[heaterman]

FWIW........Softened water is actually a bit more corrosive than unsoftened water from what I have been told. Something to do with the ion exchange in a softener. Maybe HR knows......... At any rate. When we do a closed system with large capacity we call up a local water treatment company, have them deliver jugs or drums to the job site and pump it in after first flushing the system out. The inhibitors and/or antifreeze will last far longer and you'll likely need less of the chemical additive. For semi open systems like a Garn, the recommendation is no more than half and half hard/soft. Might be worth a call to the manufacturer of your boiler to see what they recommend. At any rate, I would suggest that once you get things in operation, get in touch with a reputable water testing company that specialized or has experience with boilers and have them do a work up on your system fluid. It'll pay off in the long run and the testing is not that expensive. Far, far less money than the two days of labor we just spent draining and power washing the inside of a couple of very abused Garns.

Heaterman, you ever went back and tested pH and nitrates on garns. I tested mine and the neighbors and was surprised to fine that on mine the fill was 5.71pH and nitrates 6ppm, and after a year the pH was 8.96 with 1.2 ppm NO3. No chemicals and as you can see, acidic fill. Neighbors was 6.51pH fill and 8.9 NO3, year later 9.24pH and 3 NO3. I was surprised that the pH rose that much without any chemical additives.

When we cleaned and refilled this year we both had some "barnacles" on the steel pipes but they can right off with wash water.

By any chance, did either of these systems contain a fair amount of copper piping recently soldered together? I've seen systems that became so acidic from excess flux that the water was green with dissolved copper.

The Garns we just power washed were lined with sludge as were both HX's in the system. The water looked like a mud puddle after one of my grandkids have been in it. You can actually look down the manhole and see the bottom of the tank through the water now.

 

[brad068]

Heaterman, hardly any copper in these systems, mostly black and pex. What surprised me is that the pH rose that much. It went from the acidic side which was the well water fill to the caustic side after one year of burning. I think a pH of 8-10 is where boilers are recommended to run? I got some No burst boiler anti freeze in my solar loop and tested that, which had a pH of 8.99 with a freeze point of -13*F with my refractometer. Straight it tested a pH of 9.41 and the freeze point was off the scale. The pail says -100*F straight. I got about 250' of 1" copper in the closed solar loop and I think that I will have to inject one more pail to get the freeze point lower. Hope to get down to -30-40*F to be safe.
I thought for sure after a year of burning the water would turn even more acidic than it was at fill. But an ol' boiler man told me that when the water gets heated it will neutralize. Guess he was kinda right.

 

[Corey]

I suspect the major cause of acidity in ground water is dissolved CO2 making carbonic acid. When you heat the water you effectively degas it (watch the tiny bubbles form in a pot of hot water before it actually boils - that is dissolved gas coming out of solution) Once the CO2 is gone, the hardness minerals (calcium, magnesium, etc) are free to form weak bases which drive the pH higher.