Fresh water tank drain hole not threaded!

[alia176]

Hello all,

I have a 20g fresh water tank and I'd like to be able to drain it using a valve or a spigot. I see a hole at the bottom of the tank and it inset by about an inch. Problem is, I don't see any type of threading so that leaves me with obtaining a plug of some sort. If you have any ideas, please let me know.

Amazon has these things, that might work. https://www.amazon.com/Rubber-Winte...+Expansion+Plug+1"&qid=1584974835&s=hi&sr=1-6

 

[highwest]

What about tapping threads into the hole? What is that tank made of?

 

[mep1811]

What was originally there or you got it that way?

 

[WOODY2]

Get an expansion plug like the use in boat transoms. They are somewhat adjustable and available in different sizes. Problem solved. Oh yeah buy a spare too.

 

[alia176]

The tank is a composite material of some sort and that's the way it came. I could try drilling and tapping in that hole, got nothing to lose. Unless I drop the tank, I won't know the wall thickness.

A friction fit plug will work fine as long as the OD is correct. Here's a decent looking one.

"32232" | U.S. Plastic Corp.

www.usplastic.com

 

[Herbie]

What is that tank made of?

This is the key question. If it's ABS, Valterra makes a set of standard fittings that are meant to be welded (chemically) into their ABS tanks. They have extra-wide flanges so theirs lots of surface area to mate to the tank. I used these on my first water tank and they worked really well.

If it's steel, you might have to do something similar - find a flanged fitting to weld on, since I'm not sure if there'd be enough material thickness to tap, and you probably can't get to the inside of the tank to put a backing or compression nut on...