Think this would work for 3inch rv waste tank drain valve connected with 3inch pvc pipe?

Yes, however I would personally go with a bulkhead adapter in that case. Only because these fittings over time will inevitably crack.

On the 3 inch Uniseal, what is the outer diameter of the outer flange?

The outside diameter to the 3" Uniseal is 5".

How would this work connecting an inground rubber pond liner to a 275 gal tote also in ground using either a pipe or directly side by side?

This would work for the Tote but will not work for the liner.

So I would drill a 4in hole in order to accommodate the uniseall?

Yes. You need to drill a 4" hole. I had to use some soapy water to get the uniseal to seat into the 4" hole.

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3" UNISEAL Flexible Tank Adapter Made in the USA (Bulkhead) - 5 Pack

3" UNISEAL Flexible Tank Adapter Made in the USA (Bulkhead) - 5 Pack

Product ID: 45678160

Details

Brand
Green Goods
Color
Black
Connector Type
Adapter
Item Weight
0.3 kg
Manufacturer
The Uniseal
Material
Plastic Rubber

♻️TPE rubber resists acids & oils

⚙️Fits 3" Schedule 40 PVC pipes

🛠️65 PSI pressure rating

€ 41.42

Duties & taxes included

In stock

Sold byAmazon IrelandDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

🔧 Seal smarter, not harder — the flexible bulkhead adapter that means business.

DURABILITY THAT LASTS - Crafted from premium TPE rubber, resisting acids, oils, grease, gasoline, and sewage for long-term reliability.
UNMATCHED VERSATILITY - Seamlessly adapts to curved & irregular tank surfaces where traditional fittings fail.
EFFORTLESS INSTALLATION - Single-piece design eliminates bolts and washers—cut, insert, and push for a liquid-tight fit in minutes.
PRESSURE READY PERFORMANCE - Withstands up to 65 PSI pressure and suction, ensuring a leak-proof seal under demanding conditions.
MADE IN THE USA TRUSTED WORLDWIDE - Engineered for professionals who demand quality and efficiency in every bulkhead connection.

The 3" UNISEAL Flexible Tank Adapter is a premium, injection-molded bulkhead fitting designed for 3" Schedule 40 PVC pipes. Made in the USA from durable TPE rubber, it provides a liquid-tight seal on curved or irregular tank surfaces, resisting acids, oils, grease, gasoline, and sewage. Rated for pressures up to 65 PSI, it simplifies installation by replacing complex multi-part fittings with a single flexible unit, reducing labor and material costs while ensuring long-lasting performance.

Specifications

ASIN	B07218BRW2
Best Sellers Rank	#361,770 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #265 in Compression Bulkhead Fittings
Brand Name	Green Goods
Color	Black
Connector Type	Adapter
Customer Reviews	4.4 4.4 out of 5 stars (95)
Item Weight	0.3 kg
Manufacturer	The Uniseal Warehouse
Manufacturer Part Number	U300
Material Type	Plastic, Rubber
Model Number	U300
Number of Pieces	5
Set Name	3 Inch Uniseal Flexible Tank Adapter Bulkhead Fitting Set (5 Pack)
Size	3 Inch
Thread Size	3 inch
Thread Type	NPT
UPC	637262982661
Unit Count	1 Count

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