Building in Mexico · what I learned
Water system and plumbing for a house in Mexico: what I wish I’d understood
Before I built, I rented in Chiapas. In one small house the kitchen sink clogged so badly that part of a block wall had to be broken open to clear the fat a metre down the pipe. I didn’t want that in my own house, or a bathroom you need to leave in a hurry. But I started out thinking plumbing wasn’t worth my time to understand, and that water was something to sort out once the walls were up. That was the mistake.
If there’s one thing to know first, it’s that plumbing is much simpler than it looks once you break it down. This page is what I learned plumbing my own house in San Cristóbal de las Casas: enough to make better decisions and have useful conversations with your builders. The plumber knows the technique. You’re the one who has to live with the layout.
My water system at a glance
Cistern → pump → two roof tanks → gravity → kitchen, 2 bathrooms, 3 gas boilers
- Have the drain fittings, pipe sizes and fall checked before the floor is poured.
- Plan a way in for clearing blockages, so maintenance doesn’t mean breaking a wall.
- Choose the shower drains early, and ask how traps and vents will keep smells out.
- Pour the cistern bigger than you think you need. It’s the one part you can’t easily enlarge.
Tanks on the roof
What the tanks on Mexican roofs are for
They store water. The plastic cylinders on so many Mexican roofs are tinacos, filled from below by the street supply or by a pump, and gravity then gives the taps their pressure.
Most of the houses I rented in Chiapas had no cistern, just tanks on the roof. In the dry season the water was rationed: the supply came twice a week, sometimes less often, and the tanks had to last until it came again. In my experience of Chiapas, that scarcity, with no cistern to pump from, is the main reason you see several tanks on one roof.
A cistern is a different thing: a tank usually below ground, often concrete, that holds far more and needs a pump to lift the water up to the roof. My house has both. Rain fills the cistern, a pump fills two tinacos, and gravity does the rest. Tinacos don’t catch rain themselves, because the opening is too small, though where water is scarce you’ll sometimes see guttering run into one.
Blocked toilets
Why toilets keep blocking
Three installation choices mattered in my build, all settled before the floor is poured: the bend under the toilet, the size of the pipe, and the fall.
The bend. A tight 90° elbow gives waste a corner to catch on. A gentler 45° needs more depth under the floor, and if nobody planned the floor height, it doesn’t fit. The construction standards UNAM uses for its own buildings say the same: 45° connections on drains, with a right angle allowed only where a pipe turns from horizontal to vertical.
I have one toilet with a 90° bend, forced on me by exactly that lack of depth. In the other bathrooms I fitted a 45°, in one by raising the floor to make room, and the difference is notable: the 90° toilet is the only one in the house that blocks, now and then.
The pipe size. Four-inch is the norm here for a toilet drain, and the wider pipe is less likely to block. Builders reach for 3-inch when the walls are already up and there’s nowhere to hide the bigger pipe.
I was offered 3-inch in one bathroom that was built, before I understood any of this, with no plumbing in the walls. I said no and ran that bathroom’s pipes outside the house instead, as I have with as many water pipes as I could. It isn’t pretty, but the confidence that it works is worth the small loss in looks, and I can reach those pipes without breaking a wall or a floor.
The fall. A drain needs a steady slope so the solids travel with the water. I worked to at least 2%: two centimetres of drop for every metre of pipe. That meets or beats every minimum I’ve found; the same UNAM standards ask for 2% on drains up to 75 mm and 1.5% on larger ones, and never a level run.
I’ve never met a builder here who measured the fall. I once watched the masons on the next plot lay a rainwater drainpipe, then watched the water sit in it during the next downpour. One of my own toilet runs was under 2%, and I steepened it before the floor went down.
Changing any of these once they’re buried usually means breaking the floor. Clearing a blockage doesn’t, as long as there’s a way in: an access point (registro) on the line, or a pipe you can reach, like my outside runs.
If you’re renting or staying somewhere: a toilet that blocks again and again, rather than once, is worth having checked, because the cause may be in the pipe and not just in what went down it. Tell the owner which toilet, how often, and whether other drains slow down at the same time.
From my build · waste runs before the slab
Bathroom smells
Why bathrooms smell of drains
A drain smell means gas from the waste pipe is getting into the room, usually past a trap, sometimes through a failed seal or a leak. A trap is a bend in the drain that holds a little water to block the gas coming back up; when it’s missing, dry or not doing its job, the smell gets through.
Diagram · how a trap and vent work
In one house I rented, a pungent sulphur smell hung around the bathroom. I knew the landlady would put it down to a sensitive nose rather than pay for anything, and I had no way to point to a cause. Since then I’ve reworked what builders installed in one of my bathrooms and vented my own drains, and these are the causes I’d look for.
No vents. Venting is standard plumbing practice, set out in the US plumbing code’s chapter on vents, but in my experience builders in Chiapas don’t usually vent the main waste lines. There’s no special material, just ordinary drain pipe, but where a vent joins the waste line and where it ends both matter, so have your plumber place them.
I added three vent pipes through the roof and one through a wall, all before the floor went down. My wastewater goes to the three-stage treatment system under my garden, which is why I was adamant about venting, and I’m convinced the bathrooms would smell without it. Even so, there’s the odd day with some smell. Most days there’s none.
Shower drains with no seal. The toilet, sink and shower share the same waste line, so a smell can come up through any of them. For the showers I bought anti-odour drains, coladeras antiolores, with a flap underneath that opens to let water through and closes against smells. Give them to the builders before they pour the floor. They’re on Amazon, and they were one of the cheapest, best-value buys of the build.
A failed seal under the toilet. The ring that seals the toilet to the drain can fail, and then the smell comes from the base. Fitting one is simpler than it sounds (below). A pipe that holds waste, through a poor fall or a tight bend, can smell for the same reasons it blocks.
If you’re renting or staying somewhere: a drain that smells after the place has stood empty may just have a dry trap, where the water in the bend has evaporated. Run water into it for a minute. If the smell stays, tell the owner which drain it is and whether it gurgles when another fixture is used. That helps whoever looks at it, because gurgling can point to the venting.
Before the floor
Before the walls and floor close: what to ask
Most of the above is decided while the pipes are still visible, and if you don’t drive that conversation, it often doesn’t happen. These are the questions I’d ask the plumber or the maestro:
- Where does each fixture go, and does each toilet line up with its wall and its drain?
- What fitting is under each toilet, what size is the pipe, and what’s the fall?
- How will the traps and vents keep smells out, and are the shower drains on site yet?
- Where can I get at each line to clear a blockage without breaking anything?
Then photograph everything before the render and the floor go on. One of my better-remembered arguments on the whole build was over moving a half-built wall a few inches: as it stood, the back of the toilet wouldn’t line up with the wall and its plumbing. We moved it. Precious memories.
How much of this you chase yourself depends on how you run the build, whether with an architect or a maestro de obra or by managing it yourself. Either way, walk the water and waste routes before they’re hidden.
From my build · bathroom pipework
First-hand · a small thing that looked harder than it was
Fitting a toilet
I’d always assumed a toilet involved some elaborate installation. It doesn’t. I bought mine with no plumber on site, read the manual, and found the basic job is two holes drilled in the floor and a flange that seals the pan to the drain. Flanges run from about MX$40 to MX$600; the cheap wax one gives a good airtight seal if your floor is level, and I never saw a reason to buy the pricier plastic kind. A bead of silicone around the base finishes it. I used Sika sealant, easy to find on Amazon Mexico.
Well or rain
If your land has no water — well, rainwater, or both
My land came with no water connection at all. That’s common on the rustic plots foreigners are drawn to, and it’s one reason “cheap” land can be less cheap than it looks. For my plot, the options were catching rain or getting water out of the ground, with a water truck (pipa) as the stopgap.
My water table sits about 18 metres down, too deep for a hand-dug well, so the option was a drilled well (pozo profundo). In 2024 a local company quoted me about MX$80,000 to drill it, fit the pump and connect it to the house. Groundwater is regulated federally through CONAGUA, so check what permission you need, with them or a lawyer, before anyone drills.
Rain was my answer. Water off the lámina (tin) roof is much cleaner than runoff from the concrete roof, so the tin roof feeds the cistern that supplies the house, and the concrete roof fills separate tanks for washing clothes. That’s one reason the roof decision and the water decision go together. We haven’t needed a pipa in either dry season so far. The full catchment build is in my off-grid water guide.
The cistern
The cistern: the one part you can’t easily enlarge
Mine is a concrete-lined cisterna of about 10,000 litres. It cost MX$30,000, roughly MX$20,000 of labour and MX$10,000 of materials, and it has carried a family of four, using roughly 1,000–2,000 litres a week, through the dry seasons, though without much to spare. If I were pouring it again I’d go to 12,000–15,000 litres. Once it’s set, enlarging it means breaking concrete.
In 2025 I added a second 1,100-litre tank on the roof, filled from the cistern. It helps, but it’s a top-up, not a bigger cistern. Where that water goes, and how I’d size a cistern against the dry season, is in the off-grid guide’s water-use section.
Pump & hot water
Roof tanks (tinacos): pump up, then gravity down
Plumbing is hard to picture mostly because you never see it: the pipes are hidden in walls and floors. Mine is simpler than most, because the water only has to climb once.
A pump lifts water from the cistern to two 1,100-litre Rotoplas tanks on the roof, and from there it falls by gravity to the kitchen, both bathrooms and the boilers. No pressure pump runs every time you open a tap. The pump cost about MX$3,000; size yours to the height the water has to climb, not to the cheapest box on the shelf. The Rotoplas tank comes with an inline filter that gives the water a pass on the way up, but it isn’t a drinking-water filter.
I filter at the point of use instead of fitting a whole-house filter: shower filters, and a kitchen filter for drinking water. The full chain is in the off-grid guide’s filtering section.
For two years we switched the pump on and off by hand, climbing up to see how much was left in the tank. Since 2026 an electronic float switch does it for us, the change I describe in my story about living on rainwater.
Hot water: three gas boilers
We have three gas boilers, all fitted by the end of 2024. Two are economy de paso (on-demand) units, at MX$1,400 each, for the kitchen and the second bathroom. The main bathroom has a MX$6,000 hybrid, part storage and part de paso, with the capacity to serve another bathroom.
Hot and cold routing looks complicated on a plumber’s diagram, and those diagrams still confuse me. I’ve installed boilers and bathrooms myself anyway, by taking it one small section at a time. One cold pipe runs from the roof tank to the boiler, and the same cold line carries on past it to the bathroom. One hot pipe runs from the boiler to the bathroom. Inside the bathroom, the toilet takes only cold, while the shower and the sink take both: three places for the cold line to reach, two for the hot.
CPVC vs TuboPlus
CPVC vs TuboPlus: where each one made sense in my house
My verdict first: TuboPlus for anything exposed, above all on the roof, where its UV resistance settles it. Inside the walls either material works, and that choice is yours.
CPVC is cut with a saw and joined with a yellow glue: cheap, easy to work with, and easy to cut out and re-glue in a tight wall chase. TuboPlus is a plastic pipe whose joints are heat-fused (termofusión). It’s tougher, flexible and resistant to movement and sunlight, but it costs roughly three to four times as much for the same runs, and the fusion tool is bulky in tight spaces. I spoke to three plumbers during the build. One who installs TuboPlus will often want the whole system in it rather than mixing materials, which is a reasonable preference, as long as you know it’s a choice.
CPVC vs TuboPlus — where each earns its place
| CPVC | TuboPlus | |
|---|---|---|
| How it joins | Cut and glue | Heat-fused |
| Strengths | Cheap, simple, easy to repair | Tough, flexible, UV-resistant |
| Weaknesses | Less robust; relies on the glue joint | Dearer; needs a fusion tool; awkward in tight spots |
| Where I’d use it | Inside walls and floors, if you want cheap and easy to repair | Roof and exposed runs, or everywhere if your plumber prefers |
Fusing it myself
Fusing TuboPlus was the one job I assumed I’d never attempt. Shortly after we moved in, I needed the last connection made on the kitchen sink. The plumber, who was also a friend, didn’t have time, so he lent me his termofusor instead. It didn’t seem like a good solution, but I watched a YouTube video, had a go, and it worked. That one joint is why I bought my own: a Chinese one costs about MX$400 on Amazon, mine works well, and I’ve since used it to install a bathroom.
A plumber charges around MX$4,000 a bathroom, more with roof connections, so doing some of it yourself can save about MX$10,000. Not everyone should pick up the tool, but once you’ve made a joint yourself, you understand what you’re asking your plumber for.
Costs
Water system and plumbing costs from my house build in Mexico
What the system inside the house cost up to the end of 2024, for a two-bedroom, two-bathroom house in Chiapas: mostly what I paid, with the pump estimated. Plumbers bundle labour and materials differently and prices move, so check the lines against local quotes rather than treating them as one.
Cost breakdown — the house water system, to the end of 2024
| Item | Cost | |
|---|---|---|
| Cistern, ~10,000 L concrete-lined | MX$30,000 | ✓ |
| PumpSized to the lift from the cistern to the roof | ~MX$3,000 | ~ |
| Pump → roof tankMaterials & labour | MX$10,000 | ✓ |
| Roof tank → kitchen, 2 baths & boilersMaterials & labour (TuboPlus) | MX$12,000 | ✓ |
| In-room supply pipework2 baths + kitchen (TuboPlus) | MX$1,800 | ✓ |
| Wastewater plumbing, whole houseVery design-dependent | MX$6,000 | ✓ |
| Rooftop tank, 1,100 L Rotoplas | MX$3,800 | ✓ |
| Boilers — 3, gas2 × MX$1,400 de paso + one MX$6,000 hybrid | MX$8,800 | ✓ |
| Boiler connections + 2 shower valves | MX$2,089 | ✓ |
| Water & plumbing system | ≈ MX$77,500 | |
| Added since — not in the total | ||
| Second rooftop tank, 1,100 L2025 | not priced | |
| Electronic float switch on the pump2026 | not priced | |
Not included: getting water onto the land in the first place. If you need a deep well, my 2024 quote of about MX$80,000 sits on top of all this.
FAQ
Common questions
How much does a water system cost for a house in Mexico?
On my self-managed build in Chiapas, the water system inside the house came to about MX$77,500 up to the end of 2024: cistern, pump, roof tank, plumbing, three gas boilers, wastewater pipework and fittings, mostly at what I paid. That excludes getting water onto the land; if you need a deep well, budget for it separately.
How much does a deep well (pozo profundo) cost in Mexico?
In 2024 I was quoted about MX$80,000 to drill to around 25 metres, fit the pump and connect it to the house, with an added cost per metre if they had to go deeper. Groundwater is regulated federally through CONAGUA, so check whether you need a permit before drilling.
What size cistern do you need for a house in Mexico?
Mine holds about 10,000 litres for a family of four and cost MX$30,000. It works, but I’d pour 12,000–15,000 litres next time, because the cistern is the one part you can’t easily enlarge. How I’d size one against the dry season is in my off-grid water guide.
How does hot water work in a house in Mexico?
In mine, a cold line runs by gravity from the roof tank to each gas boiler and carries on to the bathroom, and one hot line runs from the boiler to the fixtures. The toilet takes only cold; the shower and the sink take both. I have two economy de paso boilers, for the kitchen and the second bathroom, and a hybrid for the main bathroom.
Where to go next
- The rainwater catchment, filtering and the three-stage wastewater system: off-grid water in Mexico
- What daily life on this system is like: living on rainwater
- Every other cost of the build: cost to build a house in Mexico
- All the building guides
Written by Luke Burchell
I self-managed the construction of my own house in San Cristóbal de las Casas, Chiapas, including the cistern, the gravity-fed system, the drains and vents, and the plumbing I learned to do myself. Everything here is from that build: what I paid, what I’d do again, and what I’d plan earlier.