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420 passage front head odor, advice!
2004 Hunter 420 passage, has anyone replaced the venting system for the front head. Research says the odor we are experiencing could be from an undersized hose system. We have replace hoses, macerator, changed to an electric head. No evidence of a leak in the system. 
Current hose is 5/8 inch.
If it's odor out the vent, improving the ventilation to the tank and the right tank product will help to reduce it. But unless a tank is leaking, odor from inside a holding tank is rarely if ever the source of odor INSIDE the boat, 'cuz odor from inside the tank has only one place to go: out the tank vent. The diameter of of the vent line has nothing to do with it.
It IS possible for a vent line--all the sanitation hoses--to become permeated with odor....some are a lot more resistant to it than others. There's a simple test for it: Wet CLEAN rags in HOT water--as hot as you can handle. Wrap a separate clean rag around every section of every hose including the vent line. When the hoses have cooled, remove each rag and smell it. If you can't smell anything on the rag, that hose is ok...but if you can, even faintly, that hose has permeated. The only cure for permeated hoses is new hoses, and if it's a job you only want to do once every 10 years, it's NOT the place to go cheap.
As others have mentioned, leaking fittings--even if no liquid is escaping--can be a source of odor inside a boat. Easiest way to check for those: pump out and THOROUGHLY rinse out the tank (which you should do 2-3x/season anyway). Fill it with water to which you've added red food coloring, block the vent and flush the toilet enough times to pressurize the tank. Check all the fittings including inspection ports and tank level indicators for red stains. Whether you find any or not, unblock the vent and pump or dump the tank before using the toilet.
At the risk of being accused of shameless promotion (the powers that be let me do a little of that 'cuz, you'd be buying it from them, not me) I suggest you check out the link in my signature...you'll find a lot of useful info there .
--Peggie
