---
product_id: 287871785
title: "4\" Mainline ABS Backwater Valve"
brand: "mainline"
price: "¥37443"
currency: JPY
in_stock: false
reviews_count: 11
url: https://www.desertcart.jp/products/287871785-4-mainline-abs-backwater-valve
store_origin: JP
region: Japan
---

# Integral Clean-Out for Rodding Clear Top for Easy Inspection 4" Full-Port ABS Valve 4" Mainline ABS Backwater Valve

**Brand:** mainline
**Price:** ¥37443
**Availability:** ❌ Out of Stock

## Summary

> 🚫💧 Keep your basement dry and your peace of mind intact!

## Quick Answers

- **What is this?** 4" Mainline ABS Backwater Valve by mainline
- **How much does it cost?** ¥37443 with free shipping
- **Is it available?** Currently out of stock
- **Where can I buy it?** [www.desertcart.jp](https://www.desertcart.jp/products/287871785-4-mainline-abs-backwater-valve)

## Best For

- mainline enthusiasts

## Why This Product

- Trusted mainline brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Effortless Maintenance:** Integral clean-out port allows quick rodding access, minimizing downtime.
- • **Crystal Clear Inspection:** Transparent lid lets you visually confirm valve operation without disassembly.
- • **Durable ABS Construction:** Heavy-duty, full-burial rated ABS body built to last underground and resist corrosion.
- • **User-Friendly Installation:** Fits standard 4" Schedule 40 ABS pipe with solvent-weld hubs for a secure, leak-proof fit.
- • **Ultimate Basement Protection:** Stops costly sewage backups before they start, saving you thousands in damage.

## Overview

The Mainline 4" Full-Port ABS Backwater Valve (#4963) is a patented, normally open check valve designed to prevent sewer backups in residential and commercial buildings. Featuring a clear polycarbonate lid for easy inspection and an integral clean-out for rodding, it ensures hassle-free maintenance. Constructed from durable ABS plastic, it fits standard 4" Schedule 40 ABS DWV pipes and is rated for full burial, providing reliable, long-term protection against costly sewage damage.

## Description

The Mainline #4963 Full-Port Backwater Valve is typically installed in homes or buildings that have basements, cellars, crawl spaces or area that are accessible for servicing. The normally open gate allows the sewer system to ‘vent’ any gases that may be causes by positive or negative pressures in the sewer line. The 4963 has a ‘Clear View’ top that makes inspection of the valve quick and simple for the building owner or plumber! As well, the 4963 comes with an integral clean-out for rodding the sewer lateral. Should rodding from the stack be necessary, the snake can easily pass over the open gate and be retracted with out doing any harm to the components.

Review: Saved my basement from a $15,000 disaster – 4" ABS Backwater Valve (the clear lid version) - I wish I never had to learn how important a backwater valve is, but after raw sewage backed up through the basement floor drain during a massive rainstorm two years ago (yes, the city main overflowed), I swore it would never happen again. Spent days cleaning up that nightmare. Never again. Installation Fits perfectly inline on 4" Schedule 40 ABS DWV pipe Solvent-weld hubs on both ends, just like any other ABS fitting Took me about 45 minutes with a saw, primer, and cement (I’m just a homeowner with basic plumbing skills) The clear polycarbonate lid is genius, you can actually see the flapper working and confirm it’s clean/no debris Performance Last month we had another 100-year storm event (over 6" of rain in 4 hours). City sewer was completely overwhelmed again. This valve slammed shut instantly when the pressure reversed. ZERO sewage came up the floor drain. Basement stayed bone dry while my neighbor (who didn’t have one) lost everything again. Flapper still opens freely for normal drainage, no restriction at all when flowing the correct direction. Build quality Heavy-duty ABS body, beefy rubber flapper seal Comes with a neoprene sleeve for the extension rod if you ever need to service it from above Rated for full burial, I have mine 18" underground under the concrete, zero issues Only minor nitpick It’s directional! Make sure the arrow points away from the house (away from your fixtures). I almost glued it backwards because I was rushing. Double-check before you cement. If you tie into a combined sewer or have ever had even a hint of backup, spend the $120 and 2 hours to install this thing. It’s the cheapest insurance policy you’ll ever buy. 100% worth it. Would buy again in a heartbeat. Thank you for saving my sanity (and my finished basement).
Review: Great product. Worth the money - Easy to install. Absolutely works. Had flash flooding and no worries with. y basement getting back flow from city sewer line coming into the house. Very easy access.

## Features

- Mainline Fullport Backwater Valve - 4" Normally Open - ABS
- Unique Patented Design Nearly Eliminates Failure and Allows for Easy Cleaning and Rodding
- Clear top allows for easy inspection

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B07J2QSWX4 |
| Best Sellers Rank | #231,871 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #7,180 in Pipe Fittings |
| Brand | Mainline |
| Brand Name | Mainline |
| Customer Reviews | 4.3 out of 5 stars 41 Reviews |
| Exterior Finish | Abs |
| Inlet Connection Size | 14 Inches |
| Inlet Connection Type | Full port |
| Item Dimensions | 18 x 14 x 14 inches |
| Item Weight | 5.97 Pounds |
| Item dimensions L x W x H | 18 x 14 x 14 inches |
| Manufacturer | Mainline Backflow Products Inc. |
| Manufacturer Part Number | 4963 |
| Material | Acrylonitrile Butadiene Styrene (ABS) |
| Material Type | Acrylonitrile Butadiene Styrene (ABS) |
| Model Number | ML-4963A |
| Number of Pieces | 1 |
| Number of Ports | 2 |
| Outlet Connection Size | 4 Inches |
| Size | 4" DWV |
| UPC | 696794000014 |
| Unit Count | 1.0 Count |
| Valve Type | Check Valve |

## Product Details

- **Brand:** Mainline
- **Exterior Finish:** Abs
- **Inlet Connection Size:** 14 Inches
- **Inlet Connection Type:** Full port
- **Item dimensions L x W x H:** 18 x 14 x 14 inches
- **Manufacturer:** Mainline Backflow Products Inc.
- **Material:** Acrylonitrile Butadiene Styrene
- **Number of Ports:** 2
- **Outlet Connection Size:** 4 Inches
- **UPC:** 696794000014

## Images

![4" Mainline ABS Backwater Valve - Image 1](https://m.media-amazon.com/images/I/71mnyGvfR8L.jpg)
![4" Mainline ABS Backwater Valve - Image 2](https://m.media-amazon.com/images/I/51X8sADEhXL.jpg)
![4" Mainline ABS Backwater Valve - Image 3](https://m.media-amazon.com/images/I/3146EWdbatL.jpg)
![4" Mainline ABS Backwater Valve - Image 4](https://m.media-amazon.com/images/I/41aUZHTwDyL.jpg)
![4" Mainline ABS Backwater Valve - Image 5](https://m.media-amazon.com/images/I/31RrPX+UmXL.jpg)

## Questions & Answers

**Q: if installed outside, does it need additional cleanouts before/after it or it can be snaked/unclogged thru the lid without any damage to the valve?**
A: My install was interior but buttoned in a concrete floor so I would say you don’t need to do additional clean outs.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Saved my basement from a $15,000 disaster – 4" ABS Backwater Valve (the clear lid version)
*by D***S on December 12, 2025*

I wish I never had to learn how important a backwater valve is, but after raw sewage backed up through the basement floor drain during a massive rainstorm two years ago (yes, the city main overflowed), I swore it would never happen again. Spent days cleaning up that nightmare. Never again. Installation Fits perfectly inline on 4" Schedule 40 ABS DWV pipe Solvent-weld hubs on both ends, just like any other ABS fitting Took me about 45 minutes with a saw, primer, and cement (I’m just a homeowner with basic plumbing skills) The clear polycarbonate lid is genius, you can actually see the flapper working and confirm it’s clean/no debris Performance Last month we had another 100-year storm event (over 6" of rain in 4 hours). City sewer was completely overwhelmed again. This valve slammed shut instantly when the pressure reversed. ZERO sewage came up the floor drain. Basement stayed bone dry while my neighbor (who didn’t have one) lost everything again. Flapper still opens freely for normal drainage, no restriction at all when flowing the correct direction. Build quality Heavy-duty ABS body, beefy rubber flapper seal Comes with a neoprene sleeve for the extension rod if you ever need to service it from above Rated for full burial, I have mine 18" underground under the concrete, zero issues Only minor nitpick It’s directional! Make sure the arrow points away from the house (away from your fixtures). I almost glued it backwards because I was rushing. Double-check before you cement. If you tie into a combined sewer or have ever had even a hint of backup, spend the $120 and 2 hours to install this thing. It’s the cheapest insurance policy you’ll ever buy. 100% worth it. Would buy again in a heartbeat. Thank you for saving my sanity (and my finished basement).

### ⭐⭐⭐⭐⭐ Great product. Worth the money
*by J***N on March 8, 2025*

Easy to install. Absolutely works. Had flash flooding and no worries with. y basement getting back flow from city sewer line coming into the house. Very easy access.

### ⭐ Flapper Valve found not snapped into fitting
*by C***A on September 13, 2025*

Also to address another review that said his valve would not close. that was true with mine as well, but I found out that the flapper valve was not snapped in to the fitting to allow it to rotate and close, once I snapped it in, It was operational. The seller should pay attention to quality control, make sure everything is operational before shipping.

## Frequently Bought Together

- 4" Mainline ABS Backwater Valve
- NDS 113BC* 10 in. Round Valve Box and Cover, 10 in. Height, Irrigation Control Valve Lettering, Black Box, Green Overlapping Cover, Black/Green

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*Product available on Desertcart Japan*
*Store origin: JP*
*Last updated: 2026-08-09*