Water Tanker Booking Android App: Slot Scheduling and Price Comparison

Booking a water tanker in most Indian towns still runs on phone calls and saved numbers, and the Water Tanker Booking Android App replaces that phone round with a single booking flow. A household that runs out of water today calls one or two known suppliers, asks whether a tanker is free, haggles over the price, and waits without knowing when the tanker will arrive. In the app, the customer enters the litres needed, the water source, and the delivery area, and sees live quotes from nearby suppliers side by side. Each quote shows the tanker capacity, the per-trip or per-litre price, and the earliest free slot, so the choice is made on price and timing instead of guesswork. Once booked, the app assigns a specific tanker and tracks its delivery status from dispatch to arrival.

The concept is a two-sided booking system: a customer app for ordering and a supplier dashboard for fleet management. At its core, a tanker booking is a capacity-and-route match: the litres a household needs are matched against the tankers free in that area at that hour, and the match is priced by trip or by litre. Suppliers register their tankers with capacity and water source, set per-trip and per-litre rates per delivery area, and open delivery slots on a calendar. Customers browse only the suppliers that serve their area, so every quote shown is actually bookable.

This topic is deliberately tanker-fleet specific, and it differs from a general home-service booking app in what is booked and what is priced. A home-service app matches a customer with a tradesperson and rates the person's work; this app matches litres, water source, and delivery area against a fleet of tankers, compares per-trip and per-litre prices, assigns one numbered tanker with a driver, and tracks delivery status until the water arrives. There are no tradespeople, no service ratings, and no visit scheduling here — the unit of booking is a tanker of a stated capacity carrying a stated source of water to a stated area.

The booking runs as one chain from need to delivery, with no step left to a phone call. The customer opens the app and enters litres needed, water source, and delivery area, and the app filters the supplier fleet to tankers that can serve that area with that capacity. Suppliers' quotes appear side by side with per-trip and per-litre prices and their earliest free slots, and the customer picks one quote and one slot. Booking locks that slot against the supplier's calendar and assigns a specific tanker and driver, so the same slot cannot be sold twice. The supplier confirms dispatch, the tanker status moves from confirmed to dispatched to en route, and the customer watches that status until the tanker arrives. At delivery, the customer confirms the litres received, the bill is settled against the quoted rate, and the completed order stays in history for rebooking.

1. The customer enters litres needed, water source, and delivery area in the booking screen.
2. The app filters the supplier fleet to tankers that serve that area with the chosen capacity and source.
3. Supplier quotes appear side by side, ranked cheapest first, each showing a per-trip total, a per-litre rate, and the earliest free slot.
4. The customer picks one quote and one delivery slot from the next seven days and four daily time windows.
5. Booking locks that slot on the supplier's calendar at once, and the double-booking guard removes it from the free list for every other customer.
6. The supplier confirms the booking, and the app assigns one numbered tanker and one driver to the order.
7. The order status moves from confirmed to dispatched to en route, and the customer follows it until the tanker arrives and confirms the litres received to close the order.

Builder note from the demo build: the slot grid is a 7-day × 4-slot matrix, giving 28 bookable slots per supplier (demo build count), with booked slots marked by a fixed pattern so the double-booking guard can be tested, and the price list is computed live from per-litre rates, giving 12 sample quotes across 4 suppliers × 3 capacities (demo build count).

Tech stack:

• Kotlin · Android Studio (native Android app)
• Jetpack Compose · Material 3 interface
• Firebase Authentication · phone OTP sign-in
• Cloud Firestore · bookings · slots · fleet records
• Firebase Cloud Messaging · booking and dispatch alerts
• Google Maps SDK · delivery-area selection
• Room database · offline order-history cache
• Razorpay SDK · optional UPI payment extension

Capacity-first booking, side-by-side price comparison, slot scheduling, and live delivery tracking are the four capabilities that carry this app. Capacity-first booking lets the customer choose 2,000, 5,000, or 10,000 litres and a water source — borewell, municipal supply, or RO plant water — so the tanker that arrives actually matches the household's storage and drinking needs. Price comparison puts every nearby supplier's per-trip and per-litre quote on one screen, ranked cheapest first, so the customer never has to call around for rates. Slot scheduling shows each supplier's free delivery windows for the next seven days and locks the chosen slot at booking, which ends double-booking and vague arrival promises. Live delivery tracking follows the assigned tanker through dispatch, en route, and delivered states, with the driver's contact shown once the tanker is on the road.

• [Capacity and source selection] The customer picks a tanker capacity of 2,000, 5,000, or 10,000 litres and a water source — borewell, municipal supply, or RO plant water — before any quote is shown, so every price that follows is for water the household can actually use. Implemented in the base app.
• [Side-by-side price comparison] Every supplier serving the delivery area quotes for the same capacity, and the app lists those quotes cheapest first with both the per-trip total and the per-litre rate, so unlike quantities are never compared by accident. Implemented in the base app.
• [Slot scheduling with a double-booking guard] The customer picks a day from the next seven days and one of four daily time windows, and booking locks that slot on the supplier's calendar immediately, so the same tanker-slot cannot be sold twice. Implemented in the base app.
• [Tanker assignment and delivery status] Each confirmed booking names one tanker and one driver, and the order moves through booked, confirmed, dispatched, en route, and delivered stages that the customer can follow in the app. Implemented in the base app.
• [Supplier fleet dashboard] Suppliers add tankers with capacity and source, set per-trip and per-litre rates per delivery area, open or close slots, and accept or decline incoming bookings from one screen. Implemented in the base app.
• [Order history and one-tap rebooking] Completed orders stay in the customer's history with supplier, capacity, source, slot, and bill, and any past order can be rebooked with the same details in one tap. Implemented in the base app.
• [Bill breakdown and pay-on-delivery record] The bill shows litres multiplied by the per-litre rate next to the per-trip quote, states the amount due on delivery, and records the payment once the customer confirms the litres received. Implemented in the base app.
• [UPI payment] Online payment through a UPI gateway is an optional extension for teams that want prepaid bookings; the base build settles on pay on delivery and records the payment against the quoted rate. Optional extension, not in the base build.

• Android app source code in Kotlin with Jetpack Compose, covering the customer booking flow and the supplier dashboard
• Cloud Firestore data model and security rules for suppliers, fleet, slots, and bookings
• Working demo build with sample suppliers, fleet, slots, and rates, including 12 sample quotes (demo build count)
• Price-comparison ranking and slot-locking logic with the double-booking guard
• Six-stage delivery-status workflow from booked to delivered, with cancellation as an outcome
• Project report PDF (background, pricing models, slot design, methodology, limitations)
• PPT presentation for final review
• Viva Q&A preparation document (pricing models, slot locking, Firestore structure, Android components)