Backyard Aquaponics
A place to discuss aquaponics

I've watched a lot of 'blue plastic' barrel construction videos - and most often see the more expensive through hull connections used, rather than using the bung hole manufactured into the blue barrels.

My blue barrels have two bung holes :
- one is a course thread and the plug center accepts a 3/4 inch threaded PVC.
- the other is a fine thread, and the hole itself will accept a 2 inch threaded PVC.

Is there a reason that through hull connections are used rather than the bungs in the barrel ?

Do the bung holes leak ? Are the holes not perpendicular to the end of the barrel ?

Thank you,

~X

No they don't leak, they are not in an ideal location is why you don't see APer's using them

Thanks Boss - our first system will be made from one barrel - standing vertical.
One end cut off - then flipped to face upward and set on top of the barrel bottom.
The top piece will be the grow bed and the bottom the fish tank.

Once we've learned all we can from this small system then we will build a better system that I've mentioned in other threads.

Uniseals are cheaper than through hull fittings but probably not locally available. Through hull fittings are extremely expensive. You can make your own through hull fittings and save some money if you're pressed for time and have a good selection of electrical PVC. The electrical pvc doesn't have tapered threads like the plumbing variety which is why it works better. This explains how to do it -

http://www.truetex.com/bulkhead.htm

Thanks Scotty - great tip !!!

FWIW - Some people use two seals, one on the inside and one on the outside. I'm not sure that's needed but you never know

Scotty435 aren't there concerns about off gassing when using electrical PVC? The manufacturing process isn't concerned with potability

I would be more concerned with the UV inhibitors that are added to electrical conduit...

Good point and maybe this isn't a good idea, I really don't know the answer - None of this would be approved in housing since electrical fittings are not tested and produced for potable water so it boils down to a personal choice. Here in the US, I've used the smaller ones in grow beds with no apparent consequences. It may not be worth the risk but my feeling is that the amount of off gassing would be negligible because the temperatures would be low (except in direct sunlight) but I could be wrong. According to the article I linked to there is not a difference between the two types of pvc other than the color but from what I can tell that is not always the case.

You'll also see this issue with almost every plastic that's designed to be outdoors and any non food grade ones - for example, with stock tanks made with food grade poly - and not all sites or producers will tell you that they have added UV stabilizers but some do - https://www.farmandfleet.com/products/226532-agrimaster-round-poly-stock-tank-pr928-by-behlen-country.html.

Another option that hasn't been mentioned is Uni-Seals which are cheaper than regular bulkhead fittings but you may have to order them because for most people they are tough to find locally.

@Scotty,
No worries, I have used small electrical connectors myself - mainly because there are some unique connectors that are only available as electrical conduit at your local home depot or similar store. But I do worry about it - my thinking is that they are not exposed to sunlight (used in my siphons) and not exposed to a significant acid or base so unlikely to free the UV inhibitors in the short time that I am using them. I have recently swapped them out with equivalent connectors I have found online in the white pvc.

Uniseals are great - I have used them heavily and much cheaper than bulkhead fittings...

Not much will fit a bung hole... They have a very course thread so it's not like you can just screw a plumbing fitting in it's place..