My Stenner install and bulk bleach storage strategy

JayG

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Aug 31, 2015
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Harrison, NY
Just bought a new house with a pool. Previously it had been maintained with trichlor pucks by the prior owners. I inherited a clear pool, but the CYA was >100 (probably close to 200). Being convinced by the common sense approach to pool maintenance I found here, I decided to take matters in my own hands, get rid of the pucks, fire the pool maintenance company (the prior owners were paying ~$5000/season for opening/closing, weekly maintenance), and save some $$. Plus, I like to understand how things work. So, if I was going to be through with pucks, it came down to SWG or Stenner. At 35K gallons, it seemed that our pool would be on the outer limit of what most SWG could handle (no ability to oversize the SWG by a factor of 2 or 3 for us). So the Stenner seemed like the most bullet-proof option. I've posted about my thoughts in a few posts, but I thought I would gather my approach in a new post in case others might want to try something similar.

Nothing too special about my Stenner install. I purchased the Stenner 45MPHP2 pump from Locke and will plumb it into my return line using a 1/2" x 2" schedule 40 T. I will use a Woods digital timer to control run time. The only thing that is out of the usual is my bleach storage. Pool math says that we will have to add ~72 oz of 12.5% bleach daily to bump FC by 2 ppm. I'm lazy and buying bleach weekly seemed like a chore that would foil my plans. I wanted to buy bleach in bulk and have to "refill" only once or twice per season. The rub is that bleach degrades with time (function of temperature and UV). Extrapolating from chemgeek's amazing work (http://www.troublefreepool.com/thre...bleach-over-time-by-storage-temperature/page2 post 23), I figured that low temperatures found a few feet down in the earth could provide a nice UV protected and cool storage solution for bleach.

I purchased a used food-grade HDPE 55 gallon barrel locally that has a sealed top and two-2" bungs for $35. I paid our gardener $100 to dig the hole and backfill with sand and gravel (see pic below). I paid ~$11 for a 2'x8'x3/4" sheet of rigid insulation that I used to wrap the upper part of the barrel (leaving the deepest part of the barrel in direct contact with the ground). The back fill with sand and gravel was to prevent frost heaving and distortion of the barrel. Finally, I built a frame to surround the barrel and attach a door to protect the top from rain and sun (pics below).

I put a couple gallons of Clorox into the barrel and let it sit for a day or so. I then inserted a teflon coated thermocouple into the bottom to see where the temperature settled. Currently, the air temp in lower NY was 56° F when I measured the temp of the bleach in the barrel which settled to 43-44° F (down from 55-56° F ambient when I added it). So far so good. The area in which the barrel is buried is mostly shaded so that should help as the season progresses. If my strategy works and i can keep the barrel contents between 40-50° F for the early part of the season and between 60-70° F for the latter part of the season, the degradation issue with bulk purchases will be an acceptable trade off for the convenience of only having to recharge my tank once or twice a season. If I use 72 oz/day I can get ~98 days out of a 55 gallon barrel. Our season is ~160 days. So I figure I can stock up early in the season with little worry and be good for 3 months and then buy enough to get me through the last 2 months. Since the ground will be the coldest in the early half of the season, degradation should be minimal. In the last half of the season, the barrel will be only partially full for the final two months and even if the barrel temp reaches 70° F, the degradation should only be manageable (e.g., at the end of the season, the 12.5% would be at ~10%). I'll have to see how the temperature maintains through this season (hence the $36 investment in the thermocouple).

Obviously not a solution for everyone, but for those who have the space near their equipment pad to bury a tank, I think it holds some promise. I'll do my best to keep the forum apprised of my progress.

Cheers,

Jay

IMG_0334 (1).jpg

Buried 55 gallon tank adjacent to my equipment pad.


I'll post other photos in a subsequent post...I'm getting an error message when I try to post another photo.
 
Very cool pun intended. A thought, you might want to put an aluminum foil blanket inside the box just tape as many Reynolds rap sheets as need together to roughly fill the space and place it on top before you close the lid. It will serve as a radiant barrier and slow the time it takes for the sun to saturate the space inside the box. Also would not be a bad idea top paint the lid with a light color.
 
Do you plan to drain and winterize the barrel?

I would be worried that an empty void underground will get crushed if the ground there saturates with water and freezes. Having the barrel filled with a water/RV-antifreeze mix should offer sufficient protection. The mix can be pumped out come spring time and the barrel rinsed. Any residual RV antifreeze will be destroyed by the bleach you add but if it's rinsed well it shouldn't matter.
 
Thanks!

All interesting ideas and suggestions. Matt, I was planning on filling the tank in the off season with water that I could pump out in Spring. The sand and gravel were also intended to keep frost heave from deforming the barrel. Attech, the idea of a radiant barrier under the cover and painting a light color are good. I need to seal the plywood (it is not pressure treated) to keep it from delaminating. Brown would blend in, but white would keep it cooler. I think the interior radiant barrier and a wife-friendly exterior color would be a good compromise. The site is already mostly in the shade, so direct solar effects should be reduced. As the season warms, it is the upper soil that should warm the most--that is why I insulated the upper 2' of the barrel. I'm hoping that the lower 1/3 of the barrel in direct contact with the soil dictates the temperature of the barrel contents. As I said, this is an experiment. Data will be the final arbiter.
 
I've been thinking: I was reluctant to fill up my tank until the swim season was full upon us, but the bleach I'm planning to buy is sitting at room temp at Ocean City Job Lot and won't likely be renewed for a while. I'm probably better off stashing it in my 44° F holding tank than waiting another couple of weeks before I fill up.
 
Another thought to keep in mind is that you could water the bleach down.

Degradation decreases as strength goes down.

Actually this not quite true and watering down bleach can actually increase the degradation rate.

The hypochlorite anion (OCl-) is only stable at high pH. This is why bleach has excess lye in it - so that the pH is kept above 11 (pH around 12 is optimal but generally higher % bleach needs higher pH). If you dilute the bleach with water, you will lower the pH and decrease the stability of the OCl- anion causing it to breakdown into chloride (Cl-) and oxygen gas. As well, if you add water that has any kind of metal contaminant in it (ferric iron or Fe2+) you will also increase the degradation rate.

It's best to leave the bleach undiluted.
 

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Given that I now have a place where I can store 50 gallons of bleach at <50° F, I figured I stock up and test my system. I went to a not-so-nearby Ocean State Job Lot store and bought out their stock of gallon bottles (24 @ $2.99 ea; 12.5%). I will probably wait until they get stock again and go back, but it raised the question in my mind whether one can safely mix different bleach strengths. For example, Costco has reasonably fresh 8.25% Clorox for $3.33 per 121 oz. Could I safely mix the two? I would assume so, but thought I would check with the experts. Clearly, I'd need to adjust my Stenner dosing time to compensate, but beyond some dilution of the barrel strength, anything else to worry about?
 
Ran my intake line to the cistern today. Threaded it through some flex conduit and clamped it down to avoid a tripping hazard and protect the line. I think this will work for me.

The U-turn below the pump is to keep water out of the conduit.

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At the suggestion of Atttech, I painted the cover with a light color spray paint for wood. Looks inconspicuous now.

IMG_0345.jpg

Apologies for the chaos on the equipment pad but I've been doing a wholesale revision of the pump, filter, and heating. Tools, and PVC parts are everywhere! But, it is coming together nicely.
 
The project is progressing. I had a shurflo diaphragm pump lying around and put it to use as a bleach transfer pump. I was able to transfer 24, 1-gallon jugs to the cistern in less than 15 minutes without needing to drag jugs to the equipment pad. (yes, I'm lazy, but there is no splashing like I experienced with a funnel...so clothes intact!). The better news is that the bleach temperature in the cistern is settling out around 52° F or 20° F below recent ambient temps. At that temperature, the 12.5% bleach I added should only degrade to 12.0% over 3 months (extrapolating from Chemgeek's chart: http://www.troublefreepool.com/thre...bleach-over-time-by-storage-temperature/page2 (post 23). To be sure, the ground will warm over the next 3 months, but I'll keep monitoring to see how my store of bleach fares as the season progresses. I'm still hopeful that I can get away with an early season "fill-up" of ~55 gallons and then a mid-season addition of ~30 gallons. Together, these additions should take care of the entire season.

I also invested in a monitoring system that will activate a light and an audible "chirp" when the bleach level gets 5" from the bottom of the barrel (that is one disadvantage of the buried cistern: assessing remaining volume). Given that I expect to use ~1/2" of bleach per day, the monitoring system gives me a 10-day warning before I run out entirely. Given my schedule, that should be sufficient time to restock. BTW, there are other drum volume assessment gizmos out there, but few can tolerate concentrated bleach and of those systems that can, I was worried about getting the suction feed for the Stenner or the thermometer feed tangled with the moving parts of the level meter. The system I went with is electronic with no moving parts (except an enclosed float). The batteries are supposed to last 10 years. Sweet!
 
Can you give more info on the tank level monitor?

http://www.drumalarm.com/drumalarmlowleve.html

Came from this company. Spoke with Peter, who designed a monitor that has the light and chime on a 10' cord. It is weather proof and is mounted by the stenner. The alarm triggers when the level gets less than 5" from the bottom.

IMG_0395.jpg

The device that goes in the drum has a suction arm that goes down to the bottom to which the intake for the Stenner is attached. The other tube has the float alarm and wire coming out. The arrow indicates where the Stenner intake line attaches.

IMG_0399.jpg

Not inexpensive, but it is a nice robust setup that keeps me from getting too complacent.
 
I snagged another 24 gallons of 12.5% "Mega-Shock" ($2.99/gal) from Ocean State Job Lot yesterday and pumped it into my cistern. I'm now at 50 gallons. Out of curiosity, after 24 hours of equilibration, I checked the temp of the barrel contents: 52.7° F! For the moment, I'm off the charts of Chemgeeks's degradation table. If my extrapolation is correct, after 3 months, the strength should be at ~12% rather than 12.5%. I can live with a loss of 4-5% strength given the convenience.

I have no need to add LC yet (my FC is at 21.5 ppm) but I tested the ability of the Stenner to pull from the barrel. No problems. It took a while to prime the system, but delivery rate was spot on. I'm psyched!

BTW, this is a pic of my diaphragm pump that I use to transfer bleach into the tank. I have it mounted in a weather-proof plastic box. When I add bleach to the cistern, I take out the hose from under the cistern cover and pump out the bottles from near the back of my car (no schlepping of bottles to and fro). With 25 bottles, I was done in about 10 minutes. No splashing, no waste. I'm pleased.

IMG_0396.jpg
 
Interesting. You know, come Summer, you could easily shade that cover with a picnic table or something else innocuous to eliminate the solar load. It would be interesting to see what effect that would have on the drum temperature.

Adding to Richard's thoughts...

Take a look at this product for insulating the cover Reflectix 16 in. x 25 ft. Double Reflective Insulation with Staple Tab-ST16025 - The Home Depot. I've wrapped my Hasa Liquidator which in mid summer is in direct sunlight for about 5 hrs per day and keeps the Liquidator 10 - 12 degrees cooler on the inside vs. the outside. Comes in different sizes, can be cut to size and easy to work with.
 

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