# Drainage Tank Water Level Calc — Back Calc: Slope & Footing

> Back Calc: Slope & Footing (iPhone/iPad app by Hiroaki Oosawa.)

- Source: https://appshunter.io/ios/app/drainage-tank-water-level-calc/id6798235033 (this page in markdown: same URL + `.md`)
- Developer: [Hiroaki Oosawa](https://appshunter.io/developer/6797133579)
- Category: Utilities, Productivity
- Price: Free with in-app purchases
- Age rating: 4+
- Requires: iOS 17.0 · 36 MB
- Languages: American English, Japanese
- Released: 2026-09-11
- Data updated: 2026-09-22

## What is Drainage Tank Water Level Calc?

Calculate water level from volume for drainage pits and tanks.

This app calculates the required water level by reverse-calculating from the target water volume. It supports drainage pits with frustum (sloped) shapes and footing projections, providing highly accurate results.
It helps with sanitary plumbing shop drawings, drainage pit design, and improves the efficiency of plumbing system planning and verification.


【Recommended for】

・Engineers who need to calculate the water level of drainage pits
・Users who need to determine water level from a specified volume
・Designers working with frustum (sloped) drainage pits
・Engineers who need volume calculations considering footing projections
・Professionals creating shop drawings for sanitary plumbing systems


【Key Features】

■ Reverse Calculate Water Level from Volume
Automatically calculates the required water level from the specified effective water volume.

■ Supports Frustum (Sloped) Shapes
Accurately calculates water level and volume for frustum (sloped) drainage pits.

■ Considers Footing Projections
Automatically accounts for the volume reduction caused by footing projections.

■ High-Precision Calculation
Uses an iterative calculation method to determine the water level with approximately ±0.5 mm accuracy.

■ 3D Preview
Visualize the entered dimensions and calculated water level in an interactive 3D view.


【Applications】

・Drainage pit design
・Sanitary plumbing shop drawing creation
・Plumbing system design
・Building services engineering
・Water level verification
・Volume verification

​【Evaluation Period】
All features are available for 30 days after initial installation. A lifetime license purchase is required to continue using the features after the 30-day period.

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| プレミアムアップグレード | $5.99 | one-time |


## Is Drainage Tank Water Level Calc safe?

Not enough ratings yet to assess Drainage Tank Water Level Calc.

## Is Drainage Tank Water Level Calc legit?

Drainage Tank Water Level Calc has limited verification signals. The AppsHunter Legitimacy Score for Drainage Tank Water Level Calc is 58 out of 100 points across 7 verification signals from App Store and developer data.


## Version history (last 5 releases)

### 1.0.4 — 2026-09-20

Improved internal processing.

### 1.0.3 — 2026-09-18

​Updated in-app text and purchase information, along with minor improvements.

### 1.0.2 — 2026-09-13

Improved the security and reliability of sign-in, purchases, and restore features. Also updated the trial period display and account deletion notice.

### 1.01 — 2026-09-12

Bug fixes and UI improvements for the subscription screen.

### 1.0.0 — 2026-09-11

No release notes.

## More apps by Hiroaki Oosawa

- [Humidity Calc](https://appshunter.io/ios/app/humidity-calc/id6797133577)
- [Sanitary Dft. Supt.](https://appshunter.io/ios/app/sanitary-dft-supt/id6799862269)

All apps by Hiroaki Oosawa: https://appshunter.io/developer/6797133579

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-22.*