Best way to keep water in a 1,200 gallon "open tank" clean and fresh

[Northwoodsman]

I am helping a friend install a boiler system that has a 1,200 gallon open tank in his basement.

The tank is extremly well insulated and were using a high temp PVC liner to store the water leak free.

We're also using a 40 plate HX to transfer the heat from the Paxo 40 to the storage tank and am wandering what the best water treatment is.

I'm thinking we do not want to treat it like a hot tub or pool as the chlorine/bromine will attack the copper brazing on the plate HX.

Rather, we want to treat it more like a fresh water fish tank and maintain a proper PH level.

Any help on this subject is greatly appreciated.

Thanks,

NWM.

 

[in hot water]

Seems it's a bacteria that can get started in some tanks, my former one included. My "growth started in the summer months when the tank cooled to room temperature, smelled like rotten eggs and has a black slime to it.

I suppose the key is to keep any bacteria from getting a start. I tried the typical hydronic cleaners and chemicals without any luck.

Without getting a water treatment pro and identifing the actual bug, and proper treatment, I decided time to pull the plug.

I think chlorine could stop most algae and bacteria from getting a start, Elevated temperatures, above 140F are the way to keep legionella in check.

Chlorine alone will not attack copper, as pool boilers have copper tube heat exchangers, it's more the ph or combination of ph and chlorine that will attack piping.

Watch chlorine levels with PVC, I know PVC pool piping becomes brittle in a few years if the chemicals are not kept in line.

If you are on city water, it's probably treated enough to start, but heating and evaporation will deplete the chemicals.

 

[pybyr]

I've been wondering about this, too, as I've been back to finishing and hooking up my storage (soon) and want to avoid hosting uninvited microbes in the tank.

I agree with HR's point that if you can prevent microbes from getting a start, and you have a mostly sealed lid, then that should be a good start.

I've been wondering about the concentrated hydrogen peroxide sometimes used for pool (non-chlorine pool systems) & hot tub purposes (you can get gallon jugs of 30% h2o2). Mixed into the water on the unpressurized side, it should be pretty potent at killing microbes. What's most potentially intriguing to me is that the peroxide- which is basically similar to water with an extra oxygen atom- breaks down relatively quickly into water + oxygen- and the oxygen leaves the solution as a gas. The oxygen leaves the water at a much accelerated rate if the solution is heated (as it inherently will in a storage situation). That way, you (hopefully) don't have corrosive compounds or ions (as you would with chlorine) continuing to exist over the long term in the tank and associated unpressurized plumbing. My one remaining question is whether the original "slug" of h2o2 and resulting highly (even if briefly) oxygenated water would cause an undue level of corrosion (even though you'd ideally 'shock' the system once, right before bringing it up to temperature for the first time- causing the duration of the extra-oxygenation to be brief). Anyone with more depth in metallurgy and/or water chemistry have any reactions [pun not intended] pro or con?

 

[Rory]

Of course, you could use the system year-round for domestic hot water. My furnace is cranking right now. One fire a week keeps the DHW toasty for 2 people. I checked my tank the other day and didn't notice any odors.

 

[hkobus]

Just wondering what the definition of "open" is here. If there is no lid (since you referenced an aquarium) to stop evaporation and material from entering the tank it would be a big job. Dust in the air carries a lot of moulds and bacteria that will love the tank and the changing temps. Chlorine will not last long with high temps and will stink up the house. I would look at keeping it simple and either keep it acidic with Muriatic acid or basic with TSP.
In some potable tanks we use hydrogen peroxide (35% concentrate) to keep organic material in check, it also helps oxidize any dissolved Fe and makes the water slightly acidic.

Henk.

 

[tom in maine]

We use no additives with our tanks.
The big variable here is the heat exchanger. Any chlorine will attack the stainless in the right circumstances. I believe 410 series stainless is immune to the problem, but there are no plate hx made with this material that I am aware of.

Chlorine will also attack copper if the pH is right.

We have never used additives except for corrosion inhibitors when using ferrous pumps.

Most of our tanks are used all year long, but I have never had slime buildup except when pulling the temps down to room temps with a heat pump.

 

[slowzuki]

If I recall, tanks that are heated to near boiling every so often will kill off the bacteria. There are also all kinds of chemical treatments you can use too. OWB's need the chems to survive, I'd start there.

 

[tom in maine]

Any tank temps over 160F is good enough to kill most bacteria, slime and algae.

 

[Gooserider]

Just wondering what the definition of "open" is here. If there is no lid (since you referenced an aquarium) to stop evaporation and material from entering the tank it would be a big job. Dust in the air carries a lot of moulds and bacteria that will love the tank and the changing temps. Chlorine will not last long with high temps and will stink up the house. I would look at keeping it simple and either keep it acidic with Muriatic acid or basic with TSP.
In some potable tanks we use hydrogen peroxide (35% concentrate) to keep organic material in check, it also helps oxidize any dissolved Fe and makes the water slightly acidic.

Henk.

Typically, "open" means not sealed up tight and pressurized, but well covered and sealed fairly well to minimize evaporation - just enough venting to prevent pressure build up.

I would probably also talk to the boiler chemistry people considering that one needs to be careful not to use stuff that would attack any heat exchanging plumbing that the tank water touches.

Gooserider

 

[700renegade]

Anybody ever consider ionic or colloidal silver? There is a lot of info out there on producing it yourself very economically. It is typically used for an alternative medicine approach, but the bottom line is that it is a fabulous disinfectant at low concentrations.

The term "born with a silver spoon in his mouth" was actually related to the fact that rich folks back in pre-victorian era had actual silver silverware which had a measurable effect on childhood diseases of that time. Also in the time of the covered wagon ( Oregon trail ) era, the settlers put a silver dollar or two in their wooden water barrel they carried with them to keep the goop from growing.

Just a wild thought. You could produce a lot of colloidal silver for $15 worth of electrodes.