Propane tank cleaning and design for buffertank primary loop.

huffdawg said:

Hello all, I purchased a 150 gal. lpg tank im filling it with water and 1/2 gallon of bleach right now . Is a half gal. of bleach enough and how long should I soak it for.

I will be using this tank as a primary loop / buffer tank . I will plumb in house loop which will supply dhw ,infloor and base board. shop infloor heating and dhw . And also a supply and return to storage .

Are there others on here that have plumbed this way and if so ,can you give tell me what i need besides supplies and returns from the heat loads and storage .
Dale

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Here's mine:

https://www.hearth.com/econtent/index.php/forums/viewthread/60497/#689728

Forged weldable half-couplings (less expensive that weld-o-lets and perfectly suitable in this application):

1.25" inlet/outlet top/bottom from/to storage.

1.25" inlet/outlet top/bottom from/to oil boiler.

1.25" outlet near middle for heating load supply.

1.25" inlet bottom for heating load return.

0.75" temperature wells: apex of top, a couple inches above middle outlet port, and a couple inches above bottom ports.

0.5" drain apex of bottom.

In my case the 1.25" ports are over-sized, but I had a lot of donated 1.25" pipe to work with so that's what I went with.

In my case there are tankless coils for DHW and hot tub, so that's why heating load draws from middle so that DHW and hot tub get first shot at the hottest water, and the lower half of the tank can recirculate and draw down cooler without affecting hot zone in top of tank. But even without the integrated coils, preserving a separate zone for DHW would likely be a good idea.

One mistake I made was failing to anticipate the need for two temperature sensors in one well and had to replace one well with a larger diameter one (the well, not the 0.75" fitting).

I contoured the half-couplings with a hand grinder for weldable fit, cleaned and marked the attachment points, and took it to a fabricator. Cut the holes with a hole-saw after the couplings were in place, this worked well.

Orientation of the fittings was determined by where the tank was going and where the pipes were coming from.

--ewd

Sounds like a project! I did the same as you, although with a 500 gallon tank. I have my supply and return to the house plumbed into the tank, supply to house at the top and return about 16" from the bottom. I have the feed to boiler at the bottom (dip tube) and the return from boiler at the top.

My wood boiler lines to/from the tank are "Teed" and my gas boiler is tied in there, although I don't use it.

The purists will say that one should not feed the tank and then the house, and they are right, but for me, it was simple, required little controls (my weak spot), and gave me more plumbing flexibility (multiple basements).

I used 2" pipe, hole-sawed my openings, and welded the pipes directly to the tank. Worked well with no issues, and was cheaper than the weld-o-lets, etc.

Getting rid of the mercaptan is the hardest part - I can still smell it when I was bleeding air from the system, some four months after cleaning, welding, installing, and flushing.

Good luck,

Bill

The smell is hard to get rid of... filled my tanks with 800gal of water and 6gal of bleach. Let them set for a couple days, drained them and the water in them now still smells awful. Fortunatly the ox barrier pex seems to completly block any smell from escaping into the house. Only when i draw water off do i smell the mercaptin. I have a diagram of my setup posted. It is not a perfect setup but its what I wanted for my needs and my budget! welding pipes into the tank does work well, as does welding a forged coupling cut in half (or half coupling) if you need a female port as I did

Precision chemical told me I should not have used bleach in my tank because it causes rust very rapidly.

gg

I was wondering about the corrosiveness of bleach as well, I let the tanks air out for a while befor refilling them.... I think bleach breaks down into other compounds quite quickly not sure if those compounds are as corrosive, but at the concentration we end up with surely it cant do much damage? They didnt smell bleachy by the time I put water in

huffdawg said:

How do you set up control for your boiler, buffer tank and storage tanks . I dont want the storage tanks charging while there is demand for dhw or heating loads.

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Wood boiler sends hot water to pipe at top of tanks. Wood boiler doesn't care where the hot water is going, it just makes hot water and sends it. There's a temperature sensor well up there where hot water enters/leaves the tanks.

On the buffer tank I'm using two of the three temperature sensor wells; the middle one and the bottom one. I thought I needed one at the top of the tank but I believe that was a mistake.

The bottom sensor well is used by an aquastat and by a differential temperature controller. The middle sensor is used by another aquastat. I found cheap aquastats on ebay, but you could use adjustable mechanical clixons or thermostats like for electric water heaters without the wells.

The differential controller measures the difference between the the bottom of the buffer tank and the top of storage. Pumping from storage is enabled only when the top of storage is hotter than the bottom of the buffer tank. The differential temperature controller uses thermistors and there was no problem extending one of the cables 50 feet over to the top of storage.

The pump from storage runs whenever Keep in mind that the buffer tank sensors are near the bottom of their respective buffer tank zones, so the top of each zone will normally be significantly hotter than the minimum control temperatures.

So whenever there's water coming from the boiler that is hotter than the coolest water in the buffer tank, and the buffer tank needs hotter water than it has, then the storage-to-buffer-tank pump steals it before it can get to storage, or at least before it can stay there very long.

huffdawg said:

How do you bracket other members questions in your posts Elliot?

So whenever there’s water coming from the boiler that is hotter than the coolest water in the buffer tank, and the buffer tank needs hotter water than it has, then the storage-to-buffer-tank pump steals it before it can get to storage, or at least before it can stay there very long.

Do have more than one circuit to and from storage.

Huff

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Use the quote button on the bottom of the post and then type your response underneath.

huffdawg said:

Do have more than one circuit to and from storage.

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Just one circ, if the sensor at bottom of either the DHW tank zone or heat load tank zone gets too cool, then the pump runs until both are satisfied. So it's [del]possible[/del] pretty much guaranteed one zone or the other will get hotter than it needs to be, but if it's the DHW zone there's no harm in that, and if it's the heating zone then it's just the cost of doing business, I was certainly in no mood to run two sets of lines to two tanks with two pumps and two sets of controls. The goal was to return only the coolest possible spent water back to storage, and to get my DHW and hot tub supply 50 feet closer to demand all year, so good to go there.

I didn't put a whole lot of figuring into it, just made the top DHW zone plenty big so that normally there's plenty of hot water up top in the summer to satisfy DHW demand, and thus prevents any unspent hot water circulating back to storage. And during the heating season the system spends most of the time meeting heating demand, so the DHW zone typically doesn't need to draw water from storage on its own account. 'Plenty big' for the DHW zone in my case was the top 60% of a 30 gallon tank, which seems to be working well.

Here's a sketch to give you an idea, the controls for the finished system turned out simpler and more correct:

https://www.hearth.com/econtent/index.php/forums/viewthread/61198/

Note that although my system has tankless coils suspended in the buffer tank, the same multi-zone buffer principle would apply if you were drawing from the buffer to heat an indirect DHW tank. The idea is to let the heating system recirculate until it's cool enough to return to storage while maintaining a reserve of the hottest water for DHW.

Also note than instead of a differential temperature controller you could just use an aquastat, klixon, or adjustable-disc hot water tank external thermostat at the top of storage to decide if there is water in storage hot enough to fool with.

--ewd

EW where did you find the DHW coils?

taxidermist said:

EW where did you find the DHW coils?

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I believe the only trick is knowing that they're called a 'tankless coil'. They show up pretty regularly on ebay. I had one that was part of a fossil fuel boiler that I moved over to the buffer tank so that I could get DHW from either the fossil fuel boiler or from storage. The other I got for $150 on ebay but it took a while for one to come up less than $200.

The necks and collars I got by calling a boiler manufacturer and and asking for the 'special favors' department. They were like $50 for each set, just a piece of four inch pipe and a collar with six holes in it, but at long last I'm finally getting old enough to solve some problems with a VISA card instead of spending half a day to save a hundred bucks.

And I just found a new (to me) craigslist search engine on line: allofcraigs.com. For some inexplicable reason craigslist doesn't approve of these services and likes to shut them down, so enjoy it while it lasts!

--ewd