I installed an ElectroScan on my 1983 H34. As with the other poster, I have it installed under the settee nearest the head. No smells, no floaties. In coastal waters where I sail (British Columbia), the ocean salinity will vary, especially if you sail into the Fraser River plume. I keep a small plastic container with some salt in it (the kind you buy at home depot for salting). If I am in a low salinity area (varies with seasonal river discharge) up a fjord, I throw a little bit of salt into the head and that, along with flushing and mixing in the unit does the trick. In other places, it isn't necessary. The electroscan will give you a readout in how many amps of current it is drawing. If you are at less than 14 amps, you should be adding some salt. Raritan has a salt feed system but they are crazy expensive (for what it is) and you have more vented loops to install. If you prefer, you could replace the salt solids with a brine solution.
While I was at it, I replaced ALL the hoses, got rid of the Y-valves that were there from a previous holding tank. In a H34, the install will have clean runs without places for accumulation in the hoses.
For the install, I flushed lots of water through the system first, then, in the old runs, I bought one of those cheap little drill mount pumps and used that to empty out the fluids in hoses etc. and then I tossed the pump ($10) and hoses it came with. I was replacing a very old electroscan with mechanical controller. Based on advice from here (thanks Peggy!), it was not worth fixing so I bought a new one.
I never have a full holding tank and in my cruising grounds that aren't really any no-discharge zones and here in Canada, no discharge just means no untreated sewage discharge (except in a few lakes).
I am happy with it. The only issue is that for non-sailing guests, the idea of a marine head seems enough of a mystery. Add in a button they have to push and it seems to take a few "tutorials".
