BajaNomad - Rainwater Retention and Use in Baja

Rainwater Retention and Use in Baja

JDCanuck - 3-14-2022 at 09:24 AM

We have one final goal yet to be resolved in recovering our limited rainwater on hardened surfaces at our home and storing it for future non-potable use. Site restrictions require a non visible storage system. Anyone come up with a relatively inexpensive manner of burying reservoirs to hold approximately 40,000 liters?

chippy - 3-14-2022 at 10:55 AM

https://tecnotanques.com/cisternas-rotoplas-medidas-y-precio...

This is what I have.

advrider - 3-14-2022 at 10:59 AM

We use a 1500 gallon and 1000 gallon holding tank at our cabin tract for our water supply (spring fed). They have to be underground, so they aren't crushed when we get 30 plus feet of snow. You need to keep some water in them at all times, so they don't get pushed back above ground.

It was a job, but we hand dug the holes to put the tanks in because of the remote location on a hillside in the National Forest. The tanks are available everywhere in the US and I would think Mexico. Might work for you?

JDCanuck - 3-14-2022 at 11:32 AM

Hi Lencho: Yeah, it is a lot to most people. It includes runoff from 300 M2 roofs, additional from driveways and hardened surfaces in the courtyard that we are collecting, prefiltering and so far discharging to ground. Having to keep them somewhat partially filled means we expect half that collected each year, and drawing it down half way or more during dry season.
3 to 4 large linked 10,000 liter Rotoplas tanks (as Chippy suggested, I have only found 15000l low profile tanks available in the US) so far is the best we've come up with, buried and protected with cement surrounds. Tougher self protected tanks are far more expensive but don't require cement surrounds.

[Edited on 3-14-2022 by JDCanuck]

JDCanuck - 3-14-2022 at 11:50 AM

Advrider: Thanks for the response. That does not seem like a whole lot of water storage for household use, so I assume the spring runs pretty much all year? Unfortunately, at our place the rains are very short duration and heavy when it hits for the most part. I have calculated about 50% rainwater retention of 10 cm over 600 m2 and suspect there may be excess of 20000l per year collected.
A lot of guesswork involved here.

advrider - 3-14-2022 at 12:54 PM

Yes, spring runs all year. The system feeds 14 cabin and as long as we don't have leaks we never run out. We keep it running all winter with a valve at the end of the line so that the system doesn't freeze. Our spring puts out about 2.5 gallons a minute and down to one at the end of dry years. We are off grid and everyone trys to conserve water, 60 years as still going strong.

JDCanuck - 3-14-2022 at 01:15 PM

Quote: Originally posted by advrider

Yes, spring runs all year. The system feeds 14 cabin and as long as we don't have leaks we never run out. We keep it running all winter with a valve at the end of the line so that the system doesn't freeze. Our spring puts out about 2.5 gallons a minute and down to one at the end of dry years. We are off grid and everyone trys to conserve water, 60 years as still going strong.

Which leads me to my next question: Have you considered a micro hydro generator system, or is the head and flow too low at the source?

[Edited on 3-14-2022 by JDCanuck]

advrider - 3-14-2022 at 02:54 PM

I have thought about it but need to investigate the head pressure. It might be too low but I'm not 100% sure yet. Would be awesome if it would work, I had a friend with one in a creek at his cabin and it worked really good.

4x4abc - 3-14-2022 at 03:36 PM

a one acre garden in Baja (palm trees local shrubs) uses a minimum of 1,000 liters a day
so, rainwater collection will not get you very far.

if you intend to use the rainwater for you house - the average American family uses 300 gal a day (1,100 liters)
even if you cut that in half, rain water collection in Baja will not get you very far.

JDCanuck - 3-14-2022 at 06:16 PM

Quote: Originally posted by 4x4abc

a one acre garden in Baja (palm trees local shrubs) uses a minimum of 1,000 liters a day
so, rainwater collection will not get you very far.

if you intend to use the rainwater for you house - the average American family uses 300 gal a day (1,100 liters)
even if you cut that in half, rain water collection in Baja will not get you very far.

Harald: Two of us should use 1/2 that or less when we are there as we won't be drinking any of it, but you are very correct, 40,000 liters of water isn't a whole lot if you are in full time occupancy. Rainwater tho is a whole lot softer than the 300+ ppm from the well that we have supplied to the 10000 liter cistern. Secondary reason to capture rainwater is to try and dilute that closer to 180 ppm and save on heating appliances.

[Edited on 3-15-2022 by JDCanuck]

JDCanuck - 3-14-2022 at 06:54 PM

Quote: Originally posted by 4x4abc

a one acre garden in Baja (palm trees local shrubs) uses a minimum of 1,000 liters a day
so, rainwater collection will not get you very far.

Thanks for that estimate Harald. Based on what we intend to plant, I think we can keep our plantings well watered and have enough left over to supplement our storage tanks and still be well within our water usage contract limits without paying excess fees. If I remember right, I think your pool was right around 40,000 liters volume am i close?

4x4abc - 3-14-2022 at 09:06 PM

yup, my pool is 38,000 liters (10,000 gal)
evaporation is 500 liters (125 gal) a day on average

advrider - 3-14-2022 at 09:53 PM

Wow, I never realized a pool would lose that much to evaporation. Crazy. Whatever amount you catch is good, that much less you have to pay to haul in.

JDCanuck - 3-14-2022 at 09:59 PM

Water seems to be becoming a more and more precious resource everyplace except here, where we get way more than we want.

4x4abc - 3-14-2022 at 10:19 PM

my water account allows me 17,000 liters a month for $380 pesos
above that it gets really expensive

trucked in water is $1,000 pesos for 10.000 liters

David K - 3-15-2022 at 08:42 AM

Harald, have you considered a pool cover to reduce the evaporation?

JDCanuck - 3-15-2022 at 11:26 AM

Very cheap water compared to what we pay up here, Harald. I'm sure you have looked at conservation anyplace you can tho judging from what I observed at your place. Trucked water will likely be getting far more expensive as fuel costs rise.

4x4abc - 3-15-2022 at 08:11 PM

Quote: Originally posted by David K

Harald, have you considered a pool cover to reduce the evaporation?

No

the pool is an important joy factor in my life
when warm enough, I use it several times a day
and when not in the water, I enjoy looking at it

a pool cover would destroy that experience

I have considered a pool cover for the winter to reduce heat loss over night
and night use would not effect the vista during the day much

but pool covers are ugly (especially when rolled up) and expensive
so I will add more solar collectors to increase the energy input during the day

0 sunny pool 800.jpg - 185kB

David K - 3-16-2022 at 08:56 AM

Nice! Yes, your pool was wonderful to slip into on a hot La Paz afternoon.

pacificobob - 3-17-2022 at 08:34 AM

Quote: Originally posted by JDCanuck

Hi Lencho: Yeah, it is a lot to most people. It includes runoff from 300 M2 roofs, additional from driveways and hardened surfaces in the courtyard that we are collecting, prefiltering and so far discharging to ground. Having to keep them somewhat partially filled means we expect half that collected each year, and drawing it down half way or more during dry season.
3 to 4 large linked 10,000 liter Rotoplas tanks (as Chippy suggested, I have only found 15000l low profile tanks available in the US) so far is the best we've come up with, buried and protected with cement surrounds. Tougher self protected tanks are far more expensive but don't require cement surrounds.

[Edited on 3-14-2022 by JDCanuck]

Given the collection surface area, how many gallons would be collected per inch of rain?

JDCanuck - 3-17-2022 at 12:15 PM

Hi Pacificobob: Roofs alone get 7620 liters each inch of rain, courtyard and driveway another 7620 liters for each inch of rain. Total rainfall of 4 inches about 61,000 liters per year. I think La Paz has significantly more rainfall than 10 cm per year. Only 2/3 would be recoverable, the rest lost to evaporation on lighter rainfalls. This is what results in 40,000 storeable after filtration.
Recommended cisterna installations have a large cement cap placed over them, something I want to avoid and instead looking for a fully buried type of storage container that I can cover with lightweight material or artificial grass. Cement maybe?

[Edited on 3-17-2022 by JDCanuck]

Bob and Susan - 3-17-2022 at 01:54 PM

i don't know what "baja" you guys live in but there isn't enough rain here to justify the cost of building a "water catchment"

we live in a desert...maybe....6 days of "real rain" a year
and most of that water would be "muddy"

it looks like some of these numbers are "made up"

[Edited on 3-17-2022 by Bob and Susan]

JDCanuck - 3-17-2022 at 03:33 PM

Quote: Originally posted by Bob and Susan

i don't know what "baja" you guys live in but there isn't enough rain here to justify the cost of building a "water catchment"

we live in a desert...maybe....6 days of "real rain" a year
and most of that water would be "muddy"

it looks like some of these numbers are "made up"

[Edited on 3-17-2022 by Bob and Susan]

Yes, I agree, very little rainfall, most of that in Aug and Sept on very few days and the trick to capturing is filtering out the silt before storing. Here is the climate data for La Paz:
http://www.baja-california.climatemps.com/precipitation.php
According to that table in La Paz in the months of Aug and Sept you would get (on average) 80,400 liters of water falling on 600 sq meters. Far less in other months and would not be useable. Our plan is to capture and store for reuse 40% of that each late summer and mix with well supplied water.

pacificobob - 3-17-2022 at 03:56 PM

I have 15 underground 10k liter tanks. The water that fills them once a week is ejido irrigation water. It often contains sediment. This quickly settles and I usually clean it out once every 2-3 years. Actually, I hire a kid who can fit into the tanks to do so.
The tanks are in concrete block vaults with concrete lids. A bodega is over several tanks...a vivero over the others.

JDCanuck - 3-17-2022 at 04:17 PM

Quote: Originally posted by pacificobob

I have 15 underground 10k liter tanks. The water that fills them once a week is ejido irrigation water. It often contains sediment. This quickly settles and I usually clean it out once every 2-3 years. Actually, I hire a kid who can fit into the tanks to do so.
The tanks are in concrete block vaults with concrete lids. A bodega is over several tanks...a vivero over the others.

Pacificobob: Thanks for that info. If I was to use 3 - 15K liter tanks my plan was to feed semi-filtered water to the two outside tanks and pump from the inner tank linked with a high level tie in. I had planned if i went this route to be cleaning the accumulated silt from the outer tanks about every two years. Sounds like your experience supports that idea. If I use instead one very large buried cement or fiberglas tank I would need far frequent cleaning or far better pre filtration.

pacificobob - 3-17-2022 at 05:01 PM

I have avoided concrete tanks for fear of leaks. I have a neighbor who has one that works just fine. No different than a swimming pool with a concrete roof.
I imagine the cost is similar.

Bob and Susan - 3-17-2022 at 05:07 PM

the plastic tanks WILL crack one day...
its not if its when

a concrete vault with a cement lid is a BAD idea...how do you replace a bad tank?

if water fills the vault you have to use a sump pump to empty it or MOLD arrives....

if vault is full of water the tanks could "float" if not kept FULL

bad idea

gnukid - 3-17-2022 at 08:19 PM

Quote: Originally posted by Bob and Susan

the plastic tanks WILL crack one day...
its not if its when

a concrete vault with a cement lid is a BAD idea...how do you replace a bad tank?

if water fills the vault you have to use a sump pump to empty it or MOLD arrives....

if vault is full of water the tanks could "float" if not kept FULL

bad idea

We need water to live in a desert, we use all methods available, spring water, pila, city water etc, underground tanks are often required to allow low pressure water to arrive below ground level, the cement cistern can be used on its own as a cement pool, or with plastic tanks inside, if the plastic overflows, an inexpensive sump pump can be used to refill overflow to tanks, if they crack they can removed by entering the cement cistern and cutting apart the plastic, and reinforce the cement tank for use. Mine have never cracked in twenty years, though, its seems cement cistern without plastic is most reliable and most efficient use of space and resources.

All options work, multiple separate methods work great. Underground cement with plastic inside has low wear due to reduced sun shine, I have used these for twenty years with no failure, if they fail, I remove them, If I want I replace them.

Plastic tanks inside cement, below ground is the most secure option and is recommend over plastic only or cement only for clean water, with reduced risk of contamination, and better temperature control.

I use high pressure submersible pumps below grade along with grade level pressurize regulated tanks, since they are quiet, powerful and reliable.

There is a simplified cheaper method when water pressure exists to fill above ground tanks. Put an above ground tank n cement pad in shade, put submersible pump inside, and pressure regulated switch outside. When you open the spigot the pump turns on, spigot closed the pump turns off.

[Edited on 3-18-2022 by gnukid]

JDCanuck - 3-17-2022 at 08:20 PM

Quote: Originally posted by Bob and Susan

I take it you have no cistern installed at your place? Are you on piped in water, or do you have it delivered by truck to a roof top tank? Neither of those are available at our place so we already have a buried 10K liter tank which presently holds water for the house for about 2 to 3 weeks use if the supply system goes down, which it did this past year following the storm and the tank did go empty. We did have a cement cistern back on the farm generations back that lasted quite a few decades and this would be my preference if it's available.

mtgoat666 - 3-17-2022 at 08:20 PM

There are lots of good plastic tanks designed for underground use, poly, fiberglass, etc., you just need to find a local vendor. Most new septic tanks here in usa are plastic type, they work fine for decades (plastic probably lasts longer than concrete for septic, concrete gets eaten by acid gasses)

Tank floatation is not a problem unless you have high water table. And tank floatation in high water area can be mitigated by using deadmen anchors.

Reinforced concrete, precast or cast in place, makes for good tank. Not a fan of the block and mortar tanks used in Mexico….

Get a competent contractor that builds tanks right!

JDCanuck - 3-17-2022 at 08:34 PM

Quote: Originally posted by pacificobob

I have avoided concrete tanks for fear of leaks. I have a neighbor who has one that works just fine. No different than a swimming pool with a concrete roof.
I imagine the cost is similar.

Hi Pacificobob: That was my fear too, and I have been unable to find any local sources for the precast strengthened cement storage units available in the US. Problem also with that would be getting them delivered and installed to my remote location. Your solution seems to be the most often recommended one. I'd be interested in the cost and any issues you have run into if you wouldn't mind sharing that?

Bob and Susan - 3-18-2022 at 05:46 AM

yes i too made this mistake...I have... even now... plastic tanks in a cement bunker below the ground...each tank has a shut off valve to isolate it

I originally thought the water would stay cooler...no way

the tanks cracked one at a time
The cement floor fell apart

I had to cut a BIG hole in the cement top to remove the tanks

I replaced all the tanks...replaced the floor...added a sump pump for seepage and ground vent for tide water

Even the best plastic water tanks break..,don't be fooled

Cement septic tanks are illegal...only plastic and fiberglass are acceptable....permits are required

No one should do this...tanks are better above the ground and accessible for service

dont listen to these guys...they are WRONG

JDCanuck - 3-18-2022 at 06:33 AM

Bob: Yes that a huge number of issues you ran into! Thanks for sharing and I will have to add them to my cautionary planning.

Did you install these tanks below an existing or fluctuating water table which pushed the floor up causing the tanks to flex?

Unfortunately, as much as I'd like to install above ground tanks for simplicity, it wouldn't be applicable as the existing and future tanks are gravity fed from a lower level than yours seem to be. I am definitely stuck with some kind of buried tank. I am 25 meters above sea level so tides won't affect me as they seem to have you.

mtgoat666 - 3-18-2022 at 06:50 AM

Quote: Originally posted by Bob and Susan

No one should do this...tanks are better above the ground and accessible for service

dont listen to these guys...they are WRONG

A properly built UG tank will last several decades or more.

Susan, your situation of flat lot next to ocean with shallow GW is a difficult site for UG tanks. In your particular case you are probably better off with surface tanks.

pacificobob - 3-18-2022 at 07:10 AM

Quote: Originally posted by Bob and Susan

yes i too made this mistake...I have... even now... plastic tanks in a cement bunker below the ground...each tank has a shut off valve to isolate it

I originally thought the water would stay cooler...no way

the tanks cracked one at a time
The cement floor fell apart

I had to cut a BIG hole in the cement top to remove the tanks

I replaced all the tanks...replaced the floor...added a sump pump for seepage and ground vent for tide water

Even the best plastic water tanks break..,don't be fooled

Cement septic tanks are illegal...only plastic and fiberglass are acceptable....permits are required

No one should do this...tanks are better above the ground and accessible for service

dont listen to these guys...they are WRONG

As much as you enjoy urinating on other's cornflakes...I must disagree.
Mine have been in service for 17 years without any issues. It sounds like you employed poor materials and workmanship.

JDCanuck - 3-18-2022 at 07:24 AM

Quote: Originally posted by mtgoat666

There are lots of good plastic tanks designed for underground use, poly, fiberglass, etc., you just need to find a local vendor. Most new septic tanks here in usa are plastic type, they work fine for decades (plastic probably lasts longer than concrete for septic, concrete gets eaten by acid gasses)

Tank floatation is not a problem unless you have high water table. And tank floatation in high water area can be mitigated by using deadmen anchors.

Reinforced concrete, precast or cast in place, makes for good tank. Not a fan of the block and mortar tanks used in Mexico….

Get a competent contractor that builds tanks right!

All excellent comments ! Thanks for the input. I am definitely leaning back to buried Rotoplas again as the local contractors install a lot of them fairly cheaply and the comment about cement blocks is inline with my thinking. Structural strength to resist cracking would be a big concern with cement blocks. They would also tend to leach out calcium that I am trying to reduce in the water supply.
The strengthened ribbed buried fiberglas or poly that don't require cement surrounds of that size get very expensive and I'm not sure they would even be available in that area.

mtgoat666 - 3-18-2022 at 07:36 AM

Quote: Originally posted by JDCanuck

Quote: Originally posted by mtgoat666

Don’t bury a tank that is not designed for burial!

Just because a tank is not stocked locally, does not mean it cannot be ordered.
I really doubt vendors keep UG tanks in stock. Just order a proper tank, and hire a competent/experienced contractor to install it.

TSThornton - 3-18-2022 at 08:17 AM

I live rural in the US on a low-yield well. I have a direct buried plastic tank adjacent to a pressure pump and tank subgrade in concrete rings. The rings had to be drained well with a pipe running down grade to daylight to allow sub-grade flow to move through them, but otherwise they've worked great for 22 years and counting.

JDCanuck - 3-18-2022 at 08:38 AM

Quote: Originally posted by TSThornton

I live rural in the US on a low-yield well. I have a direct buried plastic tank adjacent to a pressure pump and tank subgrade in concrete rings. The rings had to be drained well with a pipe running down grade to daylight to allow sub-grade flow to move through them, but otherwise they've worked great for 22 years and counting.

Sounds like a great well thought out design. Every location seems to have it's own issues and yours sounds both simple and inexpensive taking advantage of the slope available for drainage. How does your tank get supplied? Captured rainwater, or as a reservoir to hold well water for surge demands?
I have to admit, I find using concrete chamber rings a great idea to keep it both durable and simple. I had never thought of that. They come in very large sizes where you are located I guess?

[Edited on 3-18-2022 by JDCanuck]

TSThornton - 3-18-2022 at 01:50 PM

Yes, the rings are about 3 feet or maybe a little more in diameter, large enough to get down into to service the equipment. The cistern is filled by the well, but the well is about a 1/4 mile away and we wanted the storage to insulate against well failures (equipment or yield), and we've been glad to have it a few times over the years.

[Edited on 3-18-2022 by TSThornton]

Bob and Susan - 3-18-2022 at 02:34 PM

there is NOT enough rain in baja to install a rainwaterr tank

this is not canada or the northern usa

its just doesnt rain that much

i ve had lots of water tanks crack and leak... bad idea

mtgoat666 - 3-18-2022 at 02:49 PM

Quote: Originally posted by Bob and Susan

there is NOT enough rain in baja to install a rainwaterr tank

this is not canada or the northern usa

its just doesnt rain that much

i ve had lots of water tanks crack and leak... bad idea

Susan,
You are wrong, again!
Here in San Diego I collect my roof runoff. Works great. I know many people harvesting rain water from their roofs.
1 inch of rain on a 1000 sf2 roof is 600+ gal.
Why not collect it?

Bob and Susan - 3-18-2022 at 02:59 PM

there you go...
\

SAN DIEGO isnt in baja

most houses in san diego dont even need AC

mtgoat666 - 3-18-2022 at 03:06 PM

Quote: Originally posted by Bob and Susan

there you go...
\

SAN DIEGO isnt in baja

most houses in san diego dont even need AC

Water is water. Why not collect it?

FYI, lots of baja gets more rain than the parched and hellishly-hot desert where you live. Ensenada gets about same rainfall as San Diego, and many houses get by w/o AC.

RFClark - 3-19-2022 at 09:18 PM

I understand that the water supply in La Paz is about at it’s maximum! We have a well in Rancho Nuevo owned by the HOA. Our CONAGUA water concession is a fraction of the water coming down the arroyo most of the rest just flows back into he sea. Several of the arroyos around Todos Santos actually have surface streams that flow into the sea.

Water costs 25 pesos per M3. By splitting the gray water off about 60% of that water can be recycled, minus that lost from pools to leaks and evaporation. 8 -10K liters a month is probably the average usage.

I wonder if it’s legal to impound rain water in Mexico, most counties in California require a permit or ban the practice.

On the subject of storage tanks. Eventually they all leak! The solution is an EDPM custom liner. There’s a company in Chino CA that makes them. It cost a few hundred dollars but it's way cheaper than replacing a tank!

[Edited on 3-20-2022 by RFClark]

RFClark - 3-20-2022 at 08:55 AM

https://apple.news/AOAqowgn0STiY7e-3pH-YZQ

Arizona looks to seawater conversion project with Mexico in gulf of california.

RFClark - 3-20-2022 at 09:12 AM

We truck water in San Felipe. We have 2 - 1600 in ground plastic water tanks. The tanks are surrounded with concrete grout. One of the tanks had a root come up through the bottom! The nearest tree is 50’ away and the bottom of the tank is 7’ in the ground. I had a liner made to repair the tank after treating the ground under it with copper sulfate to stop future roots! I think you should line concrete tanks with EDPM liners from the start. That way the water is there when you need it.

JDCanuck - 3-20-2022 at 09:53 AM

Hi RFClark: Concrete lined with EPDM may be a decent alternative to a walled Rotoplas install to deal with future leaks or cracking. Did they mention what the life expectation of the EDPM might be and how easy was it to install in an existing tank?

RFClark - 3-20-2022 at 10:25 AM

A 20 year life expectancy if I remember and plastic strips w/ SS screws to hold up the sides. Just like putting a liner in a waterbed. They sell padding if your tank has a rough bottom or sides.

Here in Todos Santos they line the reservoirs with PVC sheeting to control leaks.