plumbing
I'm considering purchasing dual-flush converters for our toilets and was curious if anyone had thoughts on them. Specifically, I'd like to know:
-M
It seems as if you have an obstruction that may be floating around in the pipe or valve. Sometimes it obstructs sometimes it flows clear. I would start with changing the water valve. If this is the old style "gate" valve there are several things that can clog the line. I would replace it with a 1/4 turn ball valve. That will give you much better flow than a gate valve. You will need to shut down the water probably at the main. The old valve is probably soldered, but you could cut it off and use a compression type valve instead. "Sharkbite" is one such supplier. Although I have never used their compression valve, I have used their end caps and found them to work well.
If you can have someone hold a bucket under the pipe once you cut off the valve and then a second person turns on the water main to fill the bucket to purge the line of any debris. With cast iron pipes it is common to get clogs from rust build up. The rust may not pass the small opening in the old gate valve when you first purged the line.. Although you did not mention what type of pipes you have, if it's copper than you won't normally find rust obstructions..
Take a straw. Suck up some liquid, and put your finger over the top. Notice how the liquid doesn't fall out the bottom of the straw. That's a vacuum lock, and it is one of the reasons why you need to vent your drains. Poorly vented drains don't drain well, and you'll get clicking and bubbling. Your toilet may fail to clear the payload. So regardless of any venting in the septic tank, you need to have appropriate drain venting.
Best Answer
We put a dual flush converter on my parents toilet a year ago. It was pretty crappy (pun intended). The problem we found, was that the half flush didn't always clear everything out, and much of the time you had to double flush the half flush. When we called the manufacturer, they stated that with some old toilets, the converters don't work so well. Luckily HD was willing to take the kit back, so we returned it after a couple of weeks of trying to get it to work.
Granted, this was one of the first dual flush conversion kits, and they may be better by now, but YMMV, as it seems to depend both on the kit you get, and the toilet it is going on.
As for special considerations for septic- the less water you can use the better, so in theory converting to a dual flush should be of benefit. After our experience with my parents, for our new house (on a septic system as well) I just went with a high efficiency 1.28GPF toilet.