Overhead Tank, Underground Reservoir and Pump Planning in Salt Lake

Overhead Tank, Underground Reservoir and Pump Planning in Salt Lake

Most people planning a house in Salt Lake arrive at the water storage question late, after the plan is settled and the elevation is agreed and the contractor has started asking about bar bending schedules, and that late arrival is what makes it expensive, because an underground reservoir decides where the plot can be dug, an overhead tank decides which beams and columns carry extra load, and a pump needs a dry, ventilated, serviceable room somewhere in a layout that is already tight, so all three are plan decisions wearing plumbing clothes.

It matters more here than in many other parts of Kolkata because Salt Lake plots are regular but genuinely tight, the houses on either side have very often been built right up to the boundary already, and the supply pattern across the blocks and sectors means nearly every household is storing and pumping rather than drawing continuously, so the reservoir, the tank and the pump have to fit into the same narrow margins that light, ventilation, staircase and parking are already competing for, and every square foot you hand to water is taken away from something else.

What follows is how we work it out at Studio Contour, designing across the Salt Lake, New Town and Rajarhat belt since 2014 with 330+ buildings delivered, and the useful part is the sequence rather than the equipment, right, because once you know the order these decisions have to be taken in, you can tell quickly whether your architect has thought about water at all.

Water storage is a structure question before it is a plumbing question

An underground reservoir is not a tank you buy, it is a watertight box cast in the ground, which makes it part of the structural package and something to design alongside the foundation rather than after it. Its walls resist earth pressure from outside and water pressure from inside, its base has to be checked for uplift when the reservoir is empty and the ground around it is saturated, and its position relative to your own footings and to those of the house next door decides how deep anyone can dig without shoring. Reinforced concrete behaves well here when it is detailed for it and badly when it is treated as brickwork with a plaster coat, which is where many seepage complaints in older Salt Lake houses begin.

The overhead tank is the mirror of the same problem. Filled, it is a substantial dead load at the highest point of the building, it shifts and sloshes as it fills and empties, and it wants to land over a beam line or a column that runs all the way down rather than in the middle of a slab panel chosen because that is where the plumber found it convenient to stand. Fixing both positions on the plan is what lets the structural design absorb them quietly, and leaving them open is what produces the propped, retrofitted look you can see on plenty of roofs in the older blocks.

Where the reservoir can honestly go on a Salt Lake plot

There are only a few workable places, and each one costs you something. Under the driveway in the front margin is the usual answer, because it stays outside the footprint and remains reachable for cleaning, though the manhole cover then has to carry a car wheel rather than a foot. Under the porch keeps the cover out of the rain while tightening your parking clearance. A side margin works when the width allows it, and on a tight plot where the neighbour has already built on the boundary it usually does not. Inside the footprint is possible as part of the foundation design rather than as a hole knocked into it later, and it is the costliest route, because every inspection and desilting path then has to be built in from the start.

Separation from the drainage line and the soak pit gets settled at the same time, as does the question of which quadrant the family wants water in, since many households here are working to a vastu reading alongside everything else. We resolve that on the layout plan while it is still free to move, so our vastu compliant design work reconciles it with the structure and the drains early rather than discovering the conflict after excavation. A rebuild where the reservoir had to be fitted into the front margin while keeping a clean approach to the door is the kind of job this applies to, and Fernwood House project in Salt Lake is an example of that category of work. The manhole should also not land in the middle of the path to your front door, which is a point we come back to when we plan Entryway and Shoe Storage Design in Salt Lake Flats. If the reservoir will be shared with a co-owner or sits across a party boundary, the agreement side of that is a question for your own lawyer.

Sizing the split between below and above

Once the positions are fixed, the split can be sized, and this is where having the structure in hand pays for itself. The underground reservoir carries the buffer, so its volume follows the supply window and how many days of independence the household wants, while the overhead tank carries the peak, so its volume follows the morning draw and the fixtures upstairs. The pump sits between them and should be chosen for the actual vertical lift and the real pipe run rather than for the largest number available at the shop. The catch here is that each of these three choices moves the other two, so they are worth deciding together, with the cost consequence of each option written next to it.

Head, pressure and what the tank does to your top floor

In a G+3 or G+4 rebuild, a tank sitting just above the terrace slab often does not give the top floor enough head for a rain shower or a mixer with any real flow, so either the tank goes up on a short structure that has to be designed and detailed, or a pressure pump is planned in from the beginning. Either way it belongs in the drawings while the bathrooms are being worked out, because the fittings you choose set the pressure you need, which is why our bathroom design work and the water planning run on one drawing set rather than in sequence, and it is the same reasoning behind how we approach Master Bathroom and En-Suite Design in Salt Lake. The tank also sits on your elevation whether you planned it or not, so place it where the parapet and the massing can absorb it, and detail the overflow so water does not stain the front of the house through every monsoon.

The pump room is a real room

A pump needs ventilation, a floor drain, a proper electrical point, enough clearance to service it rather than just look at it, and some thought about noise, because a pump bolted to a slab sends its vibration into the frame and the room above hears everything. That is why we keep it out from under bedrooms and away from the quiet corner of the house, which matters when a family is also planning something like Meditation Corner Design for a Salt Lake Home. The alternative is what you find in plenty of houses, where the pump ends up in a cupboard under the stairs with no drain and no air, and gets replaced every few years because nothing about that position lets it survive.

Monsoon, groundwater and the waterproofing sequence

Salt Lake gives you a long humid stretch and a serious monsoon, and both attack stored water from different directions. The reservoir has to be waterproofed as a system and then water tested before anything is backfilled against it, because finding a leak after the driveway is laid means breaking the driveway. Groundwater pressure during the rains is what lifts an empty reservoir, so the base design and the habit of not draining it fully in the wet months both matter, and the manhole should sit slightly above the surrounding paving so runoff does not pour into your stored water.

How it reads in the Bidhannagar sanction drawings

For a plot in Salt Lake, also written Bidhan Nagar, the building authority is the Bidhannagar Municipal Corporation, while New Town sits under NKDA, and Sector V is the separate commercial and IT belt. Water storage shows up in what you submit, so the reservoir position, the drainage and septic arrangement and the terrace layout with the tank on it all have to be coherent with the coverage and setback figures that apply to your plot, and those vary by plot and have to be confirmed for yours rather than assumed from a neighbour. We prepare and run the drawings through the Bidhannagar sanction process ourselves, which is the reason we can tell you early that a reservoir position will create a problem at scrutiny. If your plot has two road frontages the margins change shape and so do your options, which is the subject of Bidhannagar Municipal Corporation Building Plan Sanction for a Corner Plot With Two Road Frontages in Salt Lake, and on taller or mixed use buildings there are fire related requirements that interact with stored water and access, covered step by step in Fire NOC Coordination Under Bidhannagar Municipal Corporation in Salt Lake: A Plot Owner's Guide.

When a different kind of provider suits you better

There is a reader for whom we are the wrong call, and it is worth being plain about it. If your building is already standing and sanctioned and all you need is a leaking tank replaced and a pump swapped, a good plumbing contractor is the right choice and paying for architectural design on top is waste. If you are putting up a minimal rental block to a formula you have used twice already, a turnkey contractor with a standard package will quote less than we will, and that standardisation is genuinely the product. The trade-off is worth understanding before you choose on price alone, because a turnkey operation earns its margin in execution, so the design drifts toward whatever the crew can build fastest, and the cheapest quote in a tender prices the visible items while reservoir waterproofing and pump room detailing are where the unpriced work hides.

Getting this settled before anything gets dug

Sumana Kumar stays on the project through sanction and through site instead of handing it to a junior once the agreement is signed, the design is worked out for your actual plot and its actual dig rather than lifted from a package, and every option is presented with its cost consequence attached so the budget moves as you decide rather than after. A Salt Lake house where the water planning was resolved on the plan before the foundation was cast is the kind of work this describes, and Sleek Modular Kitchen project in Kolkata is an example of that category of work.

At the end of the day, water storage is not the glamorous part of a house, and it is one of the few parts that reminds you every single morning whether it was planned or improvised. You can read how we work across the belt on our Salt Lake area page and what the scope covers on architecture and interior design in Salt Lake, and when you have your plot details and a rough brief ready, get in touch and we will go through the reservoir, tank and pump positions on your own plan before anything gets dug.