T&T: Vented loop

[Peggie Hall]

Steve Sipe wrote:

> ...The intake has a vented loop between the thru-hull and the 
> pump suction. Every time the pump runs, the vent on the loop opens, 
> breaking the suction to the pump, and seriously limiting the amount of 
> water for flushing. The heads never quite clear, and urinary salts have 
> a perfect environment to build. There was a minimum of 1/8" buildup on 
> the surfaces of the head. In my business, we refer to it as 
> "pi**-crete." Nasty stuff.

> Any one have a solution for the vented loop problem that will enable the 
> heads to flush properly? 

Yep...

If the toilet is a manual toilet, the vented loop is in the wrong place. 
  It belongs between the pump and the bowl...and there should be an air 
valve in the hole in the nipple on the top of the loop that only allows 
air INTO the line, nothing out.

If the toilet is electric, the vented loop is in the right place--the 
only place it can be if the toilet has an integral intake pump--so it 
requires an electric solenoid valve (essentially an electrically 
operated air valve) that's wired to the flush button installed in the 
hole in the nipple on the top of the loop.

If you'll tell me the make/model of your toilet, I'll give you the link 
to the installation instructions showing how the toilet should have been 
correctly plumbed...and can also advise you re any maintenance that 
needs to be done.

As for the buildup in the system, it's not urinary salts, but sea water 
calcium carbonates...a common problem in sea water toilets...and more of 
one in warm waters than in cooler waters because the mineral content of 
warm sea water is higher. A cupful or two of white vinegar (any more is 
just wasted) flushed through the lines weekly will prevent it in the 
discharge line...getting it into the intake is a bit more of a 
challenge, but easily done: tee a short length of hose into your intake 
line using a y-valve (a simple garden hose y-valve from any hardware 
store will work just fine). Keep a gallon milk jug aboard. When 
preparing to leave the boat, after closing the intake seacock, fill the 
jug with clean fresh water to which you've added a pint of white 
vinegar...stick the hose into it, turn the y-valve and flush the toilet. 
That'll rinse all the sea water out the entire system...intake line, 
pump, channel in the rim of the bowl AND the discharge line.

If the system is as neglected as it appears to be, the hoses are prob'ly 
permeated with sewage odor too...so once you've solved all the 
mechanical errors in the system, you'll most likely have to replace all 
the hoses too.

And fwiw, the recommended "dose" of muriatic acid in marine plumbing is 
a 12% solution.  You'll prob'ly need to use it in all your raw water 
engine hoses, water pumps, heat/ac intake etc  too.

> The long range solution will be to replace both heads with freshwater 
> flush Tecma or similar, not sure I want to spring for vacu-flush, the 
> Tecma is rated pretty high, not sure if it's worth nearly double the 
> cost to go to the vacu-flush.

It's not. The Tecma is a MUCH better toilet.

-- 
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and 
Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/books/detail-books.htm?fno=0&sku=90&cat=1304