A Kiwi couple's cruising adventures on America's Great Loop and around the coast of New Zealand

Monday, 27 July 2015

Noflex and venting

Since people often ask me, this is how Noflex works:

NOFLEX introduced into the system, being heavier than water, sinks to the bottom of the tank where anaerobic (dead bacteria sludge) concentrates. Upon contact it reacts with the sludge lifting it into the main stream releasing micro bubbles of oxygen that break up waste. This also releases the proteins out of the sludge that act as an additional source of nutrition for live bacteria. The oxygen and additional protein turn the unit into a super friendly medium for maximum growth capability.

NOFLEX is not a bacterial treatment enzyme biocide or perfumed product but a blend of chemicals that, when introduced into your sanitary system will very quickly neutralize hydrogen sulphides (unwanted odours), clean pipes and liquefy solids in your holding tank.

With the use of NOFLEX there is no need for carbon filters on vents or large quantities of product stowed in small cupboards. It is safe on plastics, cast iron and copper piping. As NOFLEX works into the tank it breaks down the organics in the wastewater, liquefying solids and greases to facilitate easy pump-outs. The spent residue from the reaction is sodium carbonate (baking soda) which helps buffer the solution for discharge to waste treatment facilities.

Raw Sewage

The bottle 1 hour after noflex has been added
1 hour after adding Noflex

the bottle 2 hours after the addition of noflex
2 hours after adding Noflex
One of the critical components of the process is that the holding tank is well ventilated, which is why the manufacturer recommends removal of vent filters which are prone to blocking. 

Since our Summer cruise (back to the Bay of Islands BTW) I have had a couple of strange happenings, one of which was the holding tank self filling with seawater by siphoning back through the macerator pump if I leave the seacock open (which I usually do). This can only happen if the discharge line that loops above the water line is full of effluent or water, and I usually ensure that the tank has completely discharged and is pumping air before I turn the pump off. And before you say "why don't you close the seacock after discharge", I always dump the tank while underway and to get to the seacock, I have to lean over the propeller shafts and couplings, which I don't like to do when they are spinning. This has been happening more often since our new year holiday, when the tank once overflowed through the vents.
The other happening was the return of a sewage smell in the master stateroom, particularly when the toilets were flushed, very reminiscent of the "pre Noflex" days. Over Easter I noticed there were rusty stains running from the vents down the side of the boat, so I cleaned them off, plus all the rust that had built up at the edges of the vent through-hull fittings. A couple of weeks later the smell was so bad in the boat that I figured there had to be something wrong, as I had been using more and more Noflex with little result. So I accessed the connections where the vent filters used to be (and noticed that there was a bit of crap inside the pipes), attached a garden hose and turned it on. For a start a mist of water came out the vent so, thinking it was clear (you can't actually see the vents themselves - they are hidden insider the through-hull fittings), I went and did the other side. Same result....a hissing mist but not a lot of water, so I presumed that's how it was supposed to be....I had never tried this before, so I didn't know what it was supposed to look like. I was about to disconnect the hose thinking the test hadn't really proved anything, when there was a "pop" from the vent and a short, yukkie brown discharge, followed by water gushing out. I then redid the other side leaving the water turned full on and after 5 minutes, sure enough, a pop, a brown discharge and pouring water. Obviously the vents had been partially blocked and may have been since we have owned the boat.....I know the vents had been flooded by the previous owner by the condition of the filters when I removed them.

So it looks like the blocked vents were causing the holding tank to pressurise during flushing and forcing effluent into the macerator discharge line, which allowed seawater to siphon back into the holding tank. It also meant that sewage gases could not vent overboard and were finding their way out through any means (probably the fittings where the filters used to be) into the bilge area of the boat and, ultimately, our stateroom.

In the 2 months since then, there has not been a hint of a smell in our stateroom, and the Admiral has commented that it is the first time the boat has been completely odour free since we have owned it.