Underground Water Storage

[stevehaigh]

i have just bought 4, 2000 liter fibreglass water tanks, the type with straight walls, wider at the top than the bottom.

i plan to put them in the ground so i can't see them. my soil is a hard packed course sand, virtually no organic matter.

so i was wondering the best/cheepest way to do it. the best way would be to build a reinforced concrete room under ground and just sit the tanks in there, but that would be quite expensive.

i was thinking maybe bury them in sand but put a couble of concrete reinforcing beams inside the tanks to stop them been crushed sideways when empty? anyone tried this?

also, should i dig one big hole for all 4 tanks or 4 smaller holes, one for each tank? the disadvantage of one big hole is, when the tanks are empty, the side walls of the sand will push all 4 together creating a lot of stress, so i probably should but some concrete braching between the tanks. the disadvantage of 4 smaller holes is it's hard to connect the water pipes between all 4 which i need to keep the water levels equal in all tanks.

anyhow, i'm rambing! any one care to share their experince, good or bad?

thanks, steve

[Jai Dee]

the best way would be to build a reinforced concrete room under ground and just sit the tanks in there, but that would be quite expensive.

Steve, I'd proceed along this way if I were you.

You're basically constructing something similar to a swimming pool, but with a concrete roof. You could use concrete bricks for the walls (as do some swimming pool builders) and construct the roof section in say 4 sections... all supported by painted steel beams, and provide access through one of the roof panels via a hatch.

I'd also have a portable submersible sump pump handy to lower into the cavity if it becomes flooded... thay're pretty cheap and handy to have around.

[Digger]

Interesting question for somebody writing a book and a website about how to build a house in Thailand. Shouldn't you be telling us the answer based on your many years of experience in the US?

Sounds like you know the answer already but you consider it too expensive which is a steel re-inforced underground bunker. But of your going to that extent, you might as well forget the fibreglass tanks and just have the concrete and steel tank made watertight and use that as your storage tank. 8,000 litres would equate to a tank 2mx2mx2m on the inside. If you went for the fibrglass tanks in the ground, your bunker would need to be a lot larger that this to contain the air surrounding the fibreglass tanks and accomodating their shape.

[Crossy]

Just a thought, do you have room in the roof space for your tanks?? No need for a pump to provide water pressure (just to get the water up there in the first place).

Standard UK practice, cold tank in the attic.

[penzman]

Why not surround each fiberglass tank with the concrete/steel rings they use to build underground water tanks. I'd then fill the gap between the tank and inside of the rings with sand. I doubt the sand inside the ring would create enough inward pressure to collapse the tanks when empty.

Edited July 1, 2005 by penzman

[chownah]

A problem you should consider is floatation. If the ground is saturated with water when the tanks are empty then they will tend to float up out of the ground...it seems strange but this does happen. I've seen pictures of commercial gasoline tanks that were improperly installed and did just that..floated up out of the ground. This problem can be solved by either creating a drainage trench around the tanks and draining the water off so that the earth around the tanks never gets saturated or by pouring a concrete mass and tieing the tanks to it. This can be a problem if you build a 'room' below grade too (the entire room can float up) but usually not because the concrete from which the room is made might be heavy enough to counteract the buoyancy...good engineering practice is to run some quick calculations on this and just pour a thicker floor to add enough weight if needed.

As to the best way to bury them....I'm still thinking about this. Alot depends on just exactly how the tanks were made. I'm not familiar with the kind you describe. Does the manufacturer have instructions on how to bury them?

[penzman]

Just a thought, do you have room in the roof space for your tanks?? No need for a pump to provide water pressure (just to get the water up there in the first place).

Standard UK practice, cold tank in the attic.

<{POST_SNAPBACK}>

Never could figure out that one... Why would you use gravity when you need water when pressure from a pump is needed to fill the tanks in the first place?

In case the electricity is out?

[Jai Dee]

Interesting question for somebody writing a book and a website about how to build a house in Thailand.   Shouldn't you be telling us the answer based on your many years of experience in the US?  

Interesting... I just did a quick google and found this and this...

Actually the developer who is building my new house at the moment will be installing underground plastic water tanks soon... I'll check with them about how they do it.

/Edit - I note the OP said his tanks were fibreglass not plastic... sure of that?

Edited July 1, 2005 by Jai Dee

[chownah]

Just a thought, do you have room in the roof space for your tanks?? No need for a pump to provide water pressure (just to get the water up there in the first place).

Standard UK practice, cold tank in the attic.

<{POST_SNAPBACK}>

Never could figure out that one... Why would you use gravity when you need water when pressure from a pump is needed to fill the tanks in the first place?

In case the electricity is out?

<{POST_SNAPBACK}>

The advantages of having a gravity feed water system (even though you need to pump it up there to begin with) are many, including 1. power failure doesn't interupt supply, 2. water pressure doesn't fluctuate rapidly like when the pump cycles, 3. you can easily have multiple supply lines so that each shower has its own line direct from the tank so you won't have that massive pressure drop when someone else turns the water on full.

By the way....how much weight would 8,000 litres of water plus tanks put on the roof?...more than 8,000 kilograms!!!! You could call it the 'hanging tanks of Damoclese!"

[penzman]

Handy for dusting the whole house at once!

[Crossy]

Just a thought, do you have room in the roof space for your tanks?? No need for a pump to provide water pressure (just to get the water up there in the first place).

Standard UK practice, cold tank in the attic.

Never could figure out that one... Why would you use gravity when you need water when pressure from a pump is needed to fill the tanks in the first place?

In case the electricity is out?

The advantages of having a gravity feed water system (even though you need to pump it up there to begin with) are many, including 1. power failure doesn't interupt supply, 2. water pressure doesn't fluctuate rapidly like when the pump cycles, 3. you can easily have multiple supply lines so that each shower has its own line direct from the tank so you won't have that massive pressure drop when someone else turns the water on full.

By the way....how much weight would 8,000 litres of water plus tanks put on the roof?...more than 8,000 kilograms!!!! You could call it the 'hanging tanks of Damoclese!"

Good point that man

We never have that much in attic tanks, 50 gallons (UK) usually. Weighs about 250kg, the roof structure is designed to take that, 8 TONS is just a little OTT

Back to the underground idea.

[stevehaigh]

Just a thought, do you have room in the roof space for your tanks?? No need for a pump to provide water pressure (just to get the water up there in the first place).

Standard UK practice, cold tank in the attic.

<{POST_SNAPBACK}>

8000 liters is a LOT of water, way too much to put in the roof.

i never used waters tanks in the US, i used city water. that's why i'm asking for help here!

[stevehaigh]

A problem you should consider is floatation.  If the ground is saturated with water when the tanks are empty then they will tend to float up out of the ground...it seems strange but this does happen.  I've seen pictures of commercial gasoline tanks that were improperly installed and did just that..floated up out of the ground.  This problem can be solved by either creating a drainage trench around the tanks and draining the water off so that the earth around the tanks never gets saturated or by pouring a concrete mass and tieing the tanks to it.  This can be a problem if you build a 'room' below grade too (the entire room can float up)  but usually not because the concrete from which the room is made might be heavy enough to counteract the buoyancy...good engineering practice is to run some quick calculations on this and just pour a thicker floor to add enough weight if needed.

As to the best way to bury them....I'm still thinking about this.  Alot depends on just exactly how the tanks were made.  I'm not familiar with the kind you describe.  Does the manufacturer have instructions on how to bury them?

<{POST_SNAPBACK}>

interesting point but i think my tanks will always be full in the wet season because i'm collecting rain water from the gutters so maybe no problem.

on the other suggestion about concrete rings, one problem is the tanks are 1.6m diameter and it's hard/expensive to get rings that big. but i did have another idea, just fill the hole around the tanks with reinforced concrete. I can fill in the corners with sand to save on concrete (money) but since i don;t need to build forms (sand walls and tank will be the forms) it should be quick and easy.

[ozzydom]

Steve,you dont mention what water you are trying to store,is it rainwater for drinking or mains supplied ordinary household aqua.?

[ozzydom]

Just a thought, do you have room in the roof space for your tanks?? No need for a pump to provide water pressure (just to get the water up there in the first place).

Standard UK practice, cold tank in the attic.

<{POST_SNAPBACK}>

Never could figure out that one... Why would you use gravity when you need water when pressure from a pump is needed to fill the tanks in the first place?

In case the electricity is out?

<{POST_SNAPBACK}>

Ceiling mounted header tanks were originally used in storeage hot water systems and even further back in fuel stove circulating hot water systems. They were standard practise when I was doing my apprenticeship. That was when pressure relief and pressure demand valves were solid brass and extremely expensive.

The copper hot water cylinders were not pressure vessels so by using a header tank they only had to cope with the pressure exerted from the gravity header tank, which was also the pressure you got at the outlet tap.

the older (but still in use today) slow combustion stove system simply worked on the principal of hot water rising.

[stevehaigh]

Steve,you dont mention what water you are trying to store,is it rainwater for drinking or mains supplied ordinary household aqua.?

<{POST_SNAPBACK}>

the tanks can fead from rain water from the gutters or bpraa-paa (government water). i hope to have enough rain water to avoid buying water at all as it's quite expensive here and highly clorinated which is bad for the garden (but helps my GF whiten up a bit I guess!).

i will use it on the usual stuff, general house and garden but not drinking of course.

since my kitchen is up 2 flights of stairs, i'm putting in a drinking water pump under the house where they drop off the water bottles. then i just press a button to get drinking water pumped to the kitchen. just like in a pub back home but without the beer!

[lopburi3]

Here in Bangkok do not find chlorine to be a problem at all with the use of two storage tanks, feed one which feeds two which feeds house. All chlorine smell and taste is gone by the time it enter home (and we use two tanks a day).