“Get the biggest cistern you can.” That’s the advice every contractor, real estate agent, and well-meaning neighbor in Los Cabos gives. It sounds logical — more water means fewer deliveries, lower cost per liter, more buffer against supply disruptions. During hurricane season, when pipas can’t run for days, a bigger cistern is peace of mind.
But nobody mentions the trade-off. A cistern that’s too big for your consumption is a cistern full of old water — water where chlorine has decayed to zero, bacteria are multiplying unchecked, and sediment has been settling undisturbed for weeks. The per-liter cost goes down, but the water quality goes down with it.
The right answer isn’t the biggest cistern. It’s the right-sized cistern — and finding it requires thinking about something most people have never heard of: turnover time.
What Size Cistern Do I Need?
For most residential properties in Los Cabos, the optimal cistern provides 7 to 14 days of water at your household’s consumption rate. This balances delivery economics (large enough that you’re not calling the pipa every three days) against water freshness (small enough that water doesn’t sit for weeks). For a typical 2–3 bedroom household with 3–4 occupants consuming roughly 400–600 liters per day, that translates to a cistern of approximately 5,000 to 10,000 liters. Properties with pools, extensive gardens, or commercial water use need more — but the turnover principle still applies.
The formula: Cistern Size = Daily Consumption × Target Turnover Days
Daily consumption for a Cabo household: approximately 150–200 liters per person per day for indoor use, plus 100–300 for irrigation, plus 200–500 for a pool. Add a buffer of 3–5 days for delivery delays. The cistern calculator does this math for you based on your specific property.
Why Sizing Is Different in Cabo
In most of Mexico’s larger cities, cistern sizing is a simpler question. Municipal water runs most of the day, the cistern is mostly a buffer for pressure drops, and it refills daily. Turnover is fast. Size matters less.
In Los Cabos, the pipa delivery model changes the equation entirely. Your cistern fills in 15 minutes and then sits for 1 to 3 weeks until the next delivery. That batch-fill pattern means your cistern size directly determines your water age, your delivery frequency, your per-liter cost, and your vulnerability to supply disruptions.
Cabo also has distinct seasonal patterns that affect sizing:
High season (November–April): Vacation properties are occupied, population swells, pipa demand increases, and delivery scheduling gets tight. Running dry during high season means emergency delivery at premium pricing — sometimes 2–3x the regular rate.
Hurricane season (August–October): Storms can disrupt pipa operations for 2–5 days. A cistern with only 3 days of buffer means you’re vulnerable. A cistern with 14 days of buffer rides out most disruptions without stress.
Summer heat (June–September): Higher temperatures mean more outdoor water use (gardens, pools), higher personal consumption, and faster water quality degradation in storage. The sizing equation shifts seasonally.
The Trade-Off Nobody Talks About
Every cistern sizing decision involves a three-way trade-off:
1. Delivery economics (favors bigger). Pipa pricing in Cabo has a strong volume discount. A 10,000L delivery costs less per liter than a 5,000L delivery. Fewer deliveries also means less scheduling hassle, less time at home waiting for the truck, and lower total delivery fees. For vacation rentals managed remotely, minimizing delivery frequency is a practical necessity.
2. Emergency buffer (favors bigger). The buffer question is simple: if your pipa delivery is delayed by 3 days (scheduling conflict, truck breakdown, hurricane), do you run dry? Running dry means an emergency delivery at premium pricing, or worse, no water at all. A larger cistern provides more days of cushion.
3. Water freshness (favors smaller). This is the overlooked factor. A larger cistern at the same consumption rate means older water. And in Cabo’s warm climate, water age has real consequences:
- Chlorine protection depletes faster at higher temperature
- Bacterial growth accelerates
- More sediment accumulates between cleanings
- Dead zones in larger tanks harbor the worst water quality
- Cleaning cost scales with cistern size
Turnover Time: The Number That Matters
Turnover time is the number of days it takes your household to use one full cistern volume. It’s the single most useful metric for cistern sizing because it directly predicts water age.
How to calculate it:
Turnover Time (days) = Cistern Capacity (liters) ÷ Daily Consumption (liters/day)What the numbers mean:
5–7 days turnover: Very fast. Your water is fresh, chlorine protection likely still active when used. But you’re calling the pipa every week, which is expensive and logistically demanding. You’ll also run dry quickly if a delivery is delayed. This is too small for most situations unless you have reliable, frequent pipa service.
7–14 days turnover: The sweet spot. Water age is manageable. You have enough buffer for delivery delays. Per-liter cost is reasonable. Cleaning frequency can be standard (every 6–12 months). Most Cabo households should aim for this range.
14–21 days turnover: Getting long. Chlorine is definitely gone before the water is used. Bacterial growth is significant. Consider more frequent cleaning (every 6 months). The delivery economics are good, but you’re paying for it in water quality.
21+ days turnover: Too long for optimal water quality. Common in oversized cisterns, vacation properties with intermittent occupancy, or large tanks installed for “peace of mind” in households with low consumption. If your turnover time is over 21 days, either increase consumption (unlikely), reduce effective cistern volume (possible by not filling to capacity), or accept more aggressive maintenance scheduling.
For vacation rentals: The challenge is that turnover time varies wildly between occupied and vacant periods. A 15,000L cistern with 4 guests consuming 800L/day has a 19-day turnover — manageable. The same cistern empty between guests has infinite water age. The solution: pre-guest flushing protocol and delivery scheduling aligned with occupancy.
Sizing by Property Type
These are guidelines based on Cabo conditions. Your actual needs depend on occupancy, water use patterns, irrigation, and pool volume. Use the cistern calculator for a precise recommendation.
Studio or 1-bedroom (1–2 people, no pool): Daily consumption: 300–500L. Recommended cistern: 5,000L. Turnover: 10–17 days. Delivery: every 2–3 weeks.
2–3 bedroom house (3–4 people, no pool): Daily consumption: 500–800L. Recommended cistern: 7,500–10,000L. Turnover: 9–20 days. Delivery: every 2 weeks.
2–3 bedroom house (3–4 people, with pool): Daily consumption: 700–1,200L (pool evaporation adds 200–500L/day in Cabo’s heat). Recommended cistern: 10,000–15,000L. Turnover: 8–21 days. Delivery: every 10–14 days.
Large home (4+ bedrooms, pool, garden): Daily consumption: 1,000–2,000L. Recommended cistern: 15,000–20,000L. Turnover: 7–20 days. Delivery: every 7–14 days. At this scale, consider two cisterns rather than one huge tank — two 10,000L cisterns allow you to alternate fills, keeping water fresher.
Vacation rental (variable occupancy): Size for peak occupancy + hurricane buffer. But recognize that during vacancy, the water sits. A 10,000L cistern for a 2BR rental balances occupied turnover (12–14 days at full occupancy) against manageable vacancy water age.
Condo (individual unit): Most condos have shared cisterns managed by the HOA, so individual sizing is not under your control. Your tinaco (typically 1,100L) is the tank you manage.
The Two-Cistern Solution
Here’s a design insight that almost nobody in Cabo implements but that solves the bigger-tank-myth perfectly: instead of one large cistern, build two smaller ones.
Two 7,500L cisterns instead of one 15,000L:
- Fill them alternately (cistern A one week, cistern B the next)
- Water age never exceeds 14 days in either tank
- You can take one offline for cleaning without losing all your water
- If one develops a crack or contamination issue, you have a backup
- Total capacity is identical, but effective water age is halved
The cost of building two smaller cisterns versus one larger one is typically 10–20% more. The water quality benefit is substantial. If you’re building new in Cabo, it’s worth discussing with your contractor.
For existing homes with an oversized cistern, the simpler solution: don’t fill it to capacity. If your 20,000L cistern results in 30-day turnover, ask the pipa driver to deliver 10,000L instead of filling to the top. You’ll pay slightly more per delivery, but your water stays fresher and your system stays cleaner.
What to Do With This Information
The free fix: Calculate your turnover time with the formula above. Just knowing the number changes how you think about your water. If it’s under 14 days, you’re in good shape. If it’s over 21 days, you have an actionable insight.
The cheap fix: Adjust your delivery schedule. Ask for partial fills to keep water age under 14 days. Schedule more frequent, smaller deliveries rather than waiting until the cistern is nearly empty. The per-liter cost is slightly higher but the quality benefit is worth it.
The right fix: Use the cistern calculator to model your optimal configuration. If you’re building or renovating, specify cistern size based on turnover time rather than “as big as possible.” Consider the two-cistern design. Combine proper sizing with inlet filtration and regular cleaning for a water system that delivers genuinely fresh, clean water.
The Math on Sizing vs. Quality
The delivery cost savings of a larger cistern are real but modest. Going from biweekly 10,000L deliveries to monthly 20,000L deliveries saves approximately annual delivery savings, expected $1,500–3,000 MXN/year. Source: local pipa pricing comparison. Update quarterly. per year.
The quality cost of oversized storage — accelerated pump wear from sediment, more frequent cleaning needed, faster filter clogging, potential appliance damage from poor water quality — can exceed annual quality cost, expected $3,000–8,000 MXN/year. Source: appliance lifecycle and maintenance cost modeling. Update annually. per year.
The first number is visible on every pipa receipt. The second number is invisible — spread across appliance replacements, extra filter cartridges, and the slow degradation of your plumbing. But it’s larger.
Frequently Asked Questions
My contractor says I need a 20,000L cistern. Is that too big? Mi contratista dice que necesito una cisterna de 20,000L. ¿Es demasiado? It depends on your consumption. For a 4+ bedroom home with pool and garden using 1,500L/day, a 20,000L cistern has a 13-day turnover — reasonable. For a 2-bedroom home with 2 occupants using 400L/day, that same cistern has a 50-day turnover — far too long. The cistern should be sized to your household, not to the maximum the lot can hold.
Can I make my existing oversized cistern smaller? ¿Puedo hacer mi cisterna existente más pequeña? You can’t physically shrink it, but you can functionally reduce it by requesting partial fills from your pipa driver. You can also install a divider wall, though this is a more involved renovation. The simplest approach: just don’t fill it all the way up.
What about hurricane preparedness? Don’t I need maximum capacity? ¿Qué hay de la preparación para huracanes? Valid concern. The solution: size your cistern for normal 7–14 day turnover, and fill to capacity before hurricane season (August–October). Yes, the water will be older during that period — but having water during a multi-day disruption is more important than optimal water age. Fill up in July, use aggressively through September, and return to partial fills after the season.
I have a pool. Does that change the sizing? Tengo alberca. ¿Eso cambia el tamaño? Significantly. Pool evaporation in Cabo’s arid climate can add 200–500 liters per day of consumption. This actually helps cistern turnover — higher consumption means faster cycling and fresher water. Factor pool consumption into your daily use estimate.
Related Pages
Understand what happens to old water: Water Age: Why Fresh Water Goes Stale in Storage — the full timeline of degradation.
Size affects sediment: Larger cisterns accumulate more sediment between cleanings. The Sediment Multiplier explains why this matters.
Get your specific number: The Cistern Size Calculator models your optimal size based on household size, property type, and consumption patterns.
Find Your Ideal Size
The Cistern Size Calculator takes your property details, occupancy pattern, and water use and gives you a specific size recommendation with turnover time analysis. Takes 2 minutes.