[Greenbuilding] Ferro cement or Plastic water tanks

[John Salmen]

Hi Dan,

 

Funny was just talking about rainwater collection today and storage/overflow issues - just looked at some figures from the last project. I live in a wet place with dry summers so the problem is always adequate storage for the dry period and how to deal with overflow in the wet period without concentrating flows and erosion problems, etc. 

 

Roof area was about 2800 sq. ft. and roof flows would be approx. 76,000 gallons a years.  with actual requirements about 28,000 gallons a year. Storage is generally based on getting through the dry months which here requires a minimum of 5000 gallons with actual monthly storage requirement being about half of that.

 

So storage is one issue – end water quality is another which generally requires some forms of filtration – rough down to fine particle and then typically some kind of bacterial treatment uv or media. Typically filtration is the overriding design/cost consideration.

 

For storage an open pond is the simplest method that can deal with both storage (including dry period storage) and overflow requirements but is highly dependent and demanding on well designed filtration – but keep in mind that filtration has to be there in any event.

 

Next simplest is stock concrete water tanks or modified concrete septic tanks provide quite clean storage and can be used in tandem with a pond for minimizing filtration requirements during wet months – drawing from the pond during dry periods. I like concrete tanks as they can have drive on lids (as part of a driveway or deck) or be the foundation for an outbuilding. 

 

Since both storage and filtration was needed the system I ended up designing for that project combined storage with filtration using both a roughing filter and a slow sand filter built into concrete tanks as both the filter and storage system. Basic idea being that both the roughing filter and slow sand filter containers could contain a large volume of water (depending on sizing) which could flow to a daily usage tank. Water would be drawn directly from roof or pond depending on flows. Since such systems are dependent on some bacterial content the pond can work. 

 

Best ponds are clay or mulch based but can take a some time to establish. An immediate pond can be made with an epdm liner.

 

I have also been looking at vertical storage (well casings) for small properties but am concerned about aquifier contamination with depth of drilling for those – seems invasive.

 

Best

John

 

 

 

 

 

 

From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Dan Barry
Sent: April-25-15 9:34 AM
To: greenbuilding at lists.bioenergylists.org
Subject: [Greenbuilding] Ferro cement or Plastic water tanks

 

As a resident of Leander Texas, we are very concerned with rainwater preservation.  35,000 gallons of storage will overflow if you trap all water off a 2500 sqfoot house(3 times a year for a Pfieffer designed house ICF built on Brown Bluff).

Can I unleash to the engineer types for green impact of:

-plastic blown tank

-metal sides with epdm liner (called Austrailian style up here)

-ferro cement, meaning  lots of rebar and wire lath and labor


 

-- thanks

Dan Barry

the humans currently consume 2000 gallons every 1.5 months from our plastic cistern.  Yes we are going to full rainwater while we do reconstruction later this year. 

 

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