rainwater collection

[mikim]

I want to collect water off the roof of my metal barn ...and in looking for poly tanks I'm finding the above ground tanks are 1/2 the price of below ground. The above ground ones I've looked at are heavy duty ....thick ...so can somebody tell me why does a buried tank have to have ribs and why can't these above ground tanks be buried? I'm obviously no engineer...but for 1/2 the money - I'm wondering about taking a chance....maybe just bury it 1/2 deep....(I need the clearance for the rain water piping)

 

[Ridgewalker]

I'm no engineer nor do I play one on TV but my guess is that the ribs are there to provide strength to keep the earth from collapsing your container over time. Pressure will come from the sides as well as the top if buried.

 

[barrybro]

Keep us posted - I have two barns and I am interested in doing the same thing.

Barry

 

[randy41]

what size tank do you have in mind?

 

[SPIKER]

as mentioned the earth will squish the un-ribbed tanks flat, over time, (if it stays 100% full it will take longer to squish it but result will be similar.) if you are in a sandy soil it will squish faster and if clay longer depending on how you place & compact the soil and when back filling tank would need to be FULL and slightly pressurized to kep earth in place.
one other option is to dig a CLOSE fitting hole lower tank into hole center up and fill with water, then pour concrete in smaller lifts to provide support for the tanks. I did this for some small catch basins I made out of 55 gallon drums. used a 3pt crete mixer and made smaller batches and didn't vibrate the crete in as that could make it FLOAT out. same as if the tank is 1/2 full and ground water rises it could cause the tank to FLOAT up and or crush in the sides...

Mark M

 

[Eagleview]

When i built my pole home i did not want the Poly tank to spoil the look of the house , so i burried it under the lounge room . After 2 years i decided to clean it out while the water level was low . Even being protected by the house , the soil has started to crush the tank walls in . They are the same profile as corrogated iron and still have bulges in the sides . Another reason why tanks that can be burried have large ribs is apart from being stronger is so that they can grab the earth and help stop them from being floated out when the loose soil around them get saturated with rain . I have had to lift out 6 ton septic tanks for local plumbers and re excavate the holes with my excavator because rain water has floated the tanks and smashed all the fittings because they did'nt fill them with water before going home . So what happens is that after a dry spell you have used most of the water in the tank and if you get a heavy downpour it can float out before it has a chance to fill .

 

[RalphVa]

I've 2 of the 330 gallon plain plastic tanks; been there about 6 years. Mine are fitted into trenches at the corner of the house and off the corner of the carriage house. They're just slid into the trenches. Terrain around here makes it easy to half bury such things and to provide walk out basements. The one off the right corner of the house is hidden by a boxwood and a tree. The one off the left rear corner of the carriage house is between the extended wall of the carriage house to retain the earth and the other side of the trench beside the retaining wall, with a small retainer on the other side of the trench past the tank. I've a wooden deck above it that I can raise on a couple of hinges and also helps to hide it.

I added 2 more barrels at 75 gallons each this spring. In total, I've 810 gallons now. The 1/2 inch of rain last night filled them all. I'd run out and had pumped out of the little stream down below with my 12v pump a couple of times. That worked well, too.

Ralph

 

[randy41]

do you use this for irrigation Ralph?
I would like to figure out how much water is discharged in t-tape per hour.

 

[mikim]

sounds like I'll be putting out some big bucks... I want this to last 20 years. What I have in my head is 2 - 5000 gallon tanks piped together for a 10,000 gallon total available storage. With conservation that could be 3 - 4 months worth of house water. It would negate watering any garden or such ... but the idea is for this to be a backup system in case my well fails and a supplemental system in the meantime. A 5,000 gallon above ground tank is 12' dia and 8' tall which only gives me 1' of fall from the gutters. With the catch & filter stuff prior to the tank ... 1' isn't enough. I"m guessing I'll need about 3' at least. If I could set that above ground tank in the dirt by 3-4' ... it would certainly help. Maybe I can take that suggestion of using some crete to shore up the sides. If I set a concrete pad under the tank, left a small crack around the edge for drainage, then built a 3' concrete retaining wall sorta thing and set the tank in that..... Kinda build a concrete bowl with holes in it for drainage and put the tank in the bowl? would that work? Below ground tanks would be preferred for both clearance, looks, space, and it would keep the water cooler in the summer heat, but they cost! Even with the above ground tanks I'm budgeting $10k for this system.

 

[RalphVa]

Randy,

My tanks are connected to about 1100-1200' of poly pipe laid through the woods. It runs down to distributors for soaker hoses on each row of the veggie garden and to old hoses to water fruit trees/shrubs. The old hoses to the trees/shrubs just have a 1/8" hole drilled in the hose at the location of each tree/shrub. I've turn-off valves to each row of 3 trees/shrubs.

In the veggie garden, there are turn-off valves to each soaker hose, too. About half of the soakers do 2 rows each. These hoses get plugged up. Every year, I poke new holes where I put seed, with an ice pick.

On each tank, there's a mechanical timer. I'll twirl it on for about 90 minutes of watering. In the past, I was forgetting to turn off the water and would run the tank dry. Each 90 minutes uses about 100 gallons through the soakers. Seems to use a little bit more to a couple lines supplying 6 trees/shrubs.

My little 12v pump does a really good job of supplying water, left on for about 3 hours. It was bought at TSC a few years ago. Pumps 1 to 5 gpm, depending on head. It'll even pump uphill the 100' to my rain tanks, but it's down to about 1 gpm to buck that 43 psi head. After 3 hours, I switch that battery to the one on my electric fence to allow it to recharge off the solar panel. It still has enough juice to run the electric fence.

Ralph

 

[randy41]

thanks for the good information. i might try that kind of thing here.

 

[EddieWalker]

Mike,

I was just thinking something similar to your idea of building a wall around the tank. I don't know if you need a bottom cement pad. I was thinking round gravel for drainage. For the walls, I was thinking retaining wall blocks. Three foot is well within the range of a do it yourselfer. If I remeber correctly, you can go 4 feet without any engineering.

What is the price difference between the two? If it's a couple grand, then digging makes allot of sense. If it's less then the cost of the block and time to dig the hole, then get the ribbed one and bury it all the way.

Eddie

 

[Treemonkey1000]

Why not disguise the above ground tank inside of a Silo or shed? You could dig out a hole to lower the height from your gutters. Then have your silo or whatever just go from the ground level up to the top of what ever size tank you use.

 

[Lasgambler]

Here in the Desert Southwest we use alot of water tanks above and below ground depending on how "Deep your pockets are". They are used for drinking water storage, either because of a low producing well, or being in and area where wells are cost prohibitive. I have installed underground tanks at several homes I have built in the area. Around here you can expect to pay about a buck a gallon for a underground, and about half that for above ground.

I have a client that wants me to use an above ground and raise it on a platform with vertical siding and a tin roof to look like a "Pettycoat Junction" water tower.

 

[jdmar]

I have been looking at this for the barn I am now building also--not for home use. Up here I really need to bury because of the winters though. I was thinking of pouring concrete around it after set in the ground. I am just using the water for equipment cleaning, hand washing, etc. I don't need to have potable or large volumes. And slightly used AG tank are cehap and available locally (auctions, etc).

A couple of numbers I have been finding since searching the net recently. You can collect about 0.6 gallons per square foot of roof per inch of rain. Remember that the "square foot" is the building footprint--i.e a 12/12 pitch collects the same as a 4/12 pitch. Many sites say expect about 80% of that for real world numbers (losses from spill over, and most "dump" the first few minutes rain to avoid the dirt/guano/etc off the roof). The US Gov also says we humans use 80-100 gallons per day! Most is toilet use, then showers. So for a large family home you need a LOT larger tank(s) than for a barn with occasional use.

Don't know if that was useful...but I found it interesting as I have been looking into this recently too. There are also a lot of "diverters" available to keep the collected water cleaner. Seems like a lot of equipment is Australlian made or designed. Hope any of this was helpful...good luck and add pics when you start.
Peter

 

[mikim]

Eddie -- like Gambler said - an underground runs about a buck a gallon .... $10,000 ... 10,000 gallon above ground is $3400 ....(5,000G tank for $1700 x 2) a bit of a difference. I like your idea of just using rock instead of a concrete base ... I have a pile of rock already from a past project. And the blocks might be good .... I'll have to price it out. It would be an awful lot of blocks....it doesn't matter what it looks like ...it'll be underground. The primary reason I was thinking concrete base was to keep the tank from shifting / tilting and breaking the pipe connections.

 

[EddieWalker]

Mike,

There are three advantages to the round gravel over a cement pad that I can think of. First, it will drain water. A little flooding probably wouldn't be a big deal for this, but you still want the water to drain as quickly as possible. Off the top of my head, I'd think 6 to 8 inches of gravel would work.

Second, is the rock will spread the load and wont move on you regardless of soil conditions. A concrete pad may do this if not engineered properly. With 5,000 gallons and water weighing around 8 pounds a gallon, 40,000 pounds of water on the cement pad becomes a number that exceeds common building methods. If your soil has allot of movement when it dries, cracks, expands and freezes, then keeping a cement pad flat and level will be even more complicated.

Third, gravel is very easy to install.

As for the block and your depth, I just had another thought. Why use anything? Slope the dirt back so that you can mow it, plant grass and leave it alone. It's more dirt to remove, but that's allot cheaper then buying allot of block or pouring a retaining wall.

If I understand the problem correctly, all you need is for the tank to be partially below grade and not have any preasure against the walls from the surrounding soils. I think a gravel pad and sloped walls is a cheap, easy way to do this.

Eddie

 

[ampsucker]

i, too, have considered various incarnations of the rain water storage scenario. it always comes down to me finding some places more economical to divert the funds to, and it never gets done. here are the problems i see that need to be overcome:

- pre filter to keep dirt leaves etc out.
- insect filter to keep skeeters and others from either setting up a breeding ground or going in after water and dying inside the tank.
- overflow diversion once the tanks gets full so you have full flow of your guttters to a good location after filling.
- if mounted above ground, you can gravity drain but have to deal with the unsightly tank and freezing in the winter
- if mounted below ground, you have to pump it out, it's more difficult to clean out periodically and the initial cost is higher for the structurally reinforced tank you have to bury.
- if used as a back up source of drinking water, you still have to purify it because a screen filter will keep debris out but not bacteria, other microbes, cysts and eggs found in bird doo doo.
- if used as a source of irrigation, better than chlorinated or city water but hardly worth the cost in our area.

Running the numbers, a gallon of water from our municipality costs somehwere in the range of .5 to 1 cent per gallon. Thus, 5,000 gallons costs 25 to 50 bucks. It takes a lot of months to recover the cost of installing and maintaining a rain water collection system, ergo, it never gets done around here.

If you just want to irrigate, dig a pond and sink a sump pump in it. It's cheaper and easier to maintain and the natural biodiversity keeps things in check. If you want to store drinking water, add a cheap storage tank of the correct size someplace out of the way, fill it with well/city water and cap it. Periodically drain it (use it on the garden or lawn, of course) and refill. Done.

amp

 

[RalphVa]

I'd have a couple problems with one below grade: 1) need to pump it out with a sump pump or you'll always be facing pump suction problems, 2) can't really drain it for the winter (maybe you don't with it below grade though).

I bought a big wet/dry vac. It works well, with a couple of the plastic "snouts" put together, to clean out the tanks. I don't filter out any stuff that comes off the roofs. I've also used a little portable air tank to back blow the tanks, to clear them of some silt or algae blocking the outlet.

If you have to put below grade, I'd put it into a hole with some sloped walls. Or put above grade and use some scrubs to hide it. Maintenance would be whole lot easier on an above grade one. You have to drain them for the winter though. My outlet spigot is in a big plug that screws out for the winter.

On the inlet, I just have a "Y" tee (3 to 4 inch) dropping into the tank on the down side of the "Y". When the tank is full, water just flows straight through the tee. Of course, it also overflows the tank.

For mosquitoes, just add a 1/2 cup of kerosene a day or so after the tank is filled each time. Reminds me. Need to do this on mine, as that first 1/2 inch of rain filled them all again. This really hot weather can bring the skeeters out.

Ralph

 

[mikim]

Eddie - I'd love to do the slope idea - but that would take an additional 12' of radius that I don't have in the location.
amp:
1. check 2.check 3. check 4. non issues 5. another non issue -- I don't plan on cleaning 5,000 gal tanks on any kind of basis. 6. check ... I do that with the well water also. price per gal of water ..... what's it worth if you have no supplier and it's all up to you to provide or not have any period?