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Old 12-03-2020, 09:05   #1
TCL
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Join Date: Jul 2011
Location: Waveland, MS
Boat: 1979 Morgan 461, 46' sloop
Posts: 63
Vented Loop Question - AWL Head + BWL MSD

OK, if this is a dumb question, don't give me too much grief.

The question is whether I need vented loops both before AND after my Electroscan MSD I.

I have a Raritan PH Powerflush head and a Raritan Electroscan MSD. The head is installed above the waterline, the Electroscan is below the waterline. So my question is really whether the loop between head and MSD is needed.

I've attached four photos:
illustration from Raritan PH Powerflush manual showing two installations--head above waterline and head below waterline;
photo of the two vented loops currently in the system;
photo showing location of the Electroscan--the unused(capped) thru-hull circled in blue is right at the waterline; and
exterior view showing same thru-hull (this thru-hull has nothing to do with the system; I'm only highlighting it to show the location of the MSD in relation to the waterline).

TO BE CLEAR: I am not installing now for the first time. I installed the system a couple of years ago, and I installed it with two vented loops, one before and one after the MSD. It has been working fine since. I doing some cleaning to the system and wondered whether it could be simpler/more streamlined. I might replace the hoses, and I might even consider switching to Sch40 PVC.

But my primary question now is whether the two long runs with loops are necessary, in the event that eliminating some of the distance would improve performance (and I don't know whether that would be the case).
The installation manual diagram shows, for an AWL installation, one vented loop between the head (AWL) and the MSD (AWL); but, for a BWL installation, shows vented loops between the head (BWL) and MSD (BWL). My installation is a combination--head AWL and MSD BWL.

I would keep the vented loop between the MSD and discharge thru-hull. So the question is whether I can eliminate the vented loop between the head and the MSD.

I didn't find an answer in Peggie Hall's book. Thinking maybe peghall might be able to help on here.

Thanks
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Old 12-03-2020, 14:16   #2
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Re: Vented Loop Question - AWL Head + BWL MSD

You rang?


The question is whether I need vented loops both before AND after my Electroscan MSD I have a Raritan PH Powerflush head and a Raritan Electroscan MSD. The head is installed above the waterline, the Electroscan is below the waterline. So my question is really whether the loop between head and MSD is needed.

The answer is "prob'ly not" The reason for the vented loop between the toilet and the ES is to prevent ES contents from running back to the toilet...necessary when the toilet is at the same level or below the ES. On a sailboat, heeling can change their relative positions even if the ES is below the toilet...it depends on how far below the toilet it is. Your toilet is above waterline and it appears from your photos that you have a very deep bilge, so unless the ES is mounted high in the bilge it's unlikely that a Morgan ever heels enough to need the vented loop between the toilet and and the ES.

Without knowing how far above waterline either of your vented loops are, you may also be able to shorten the amount hose needed for the one between the ES and the thru-hull it's higher than 6-8" above waterline at max heel.


On another note...if you're finding it necessary to replace hoses after only a few years, I suggest you go with Raritan SaniFlex hose RaritanSaniFlex hose There's yet to be a single reported odor permeation (or any other) failure in the 10 years it's been on the market...I've yet to hear of any either, and I'm pretty sure I would have...plus it has the added advantage of being so flexible it can be bent like a hairpin without kinking, which makes it a whole lot easier to work with than hard PVC. Defender has it on sale for < $10/ft.

Thanks for buying my book!

--Peggie
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Old 12-03-2020, 17:15   #3
TCL
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Re: Vented Loop Question - AWL Head + BWL MSD

Thanks, Peggie! I confess I had not thought about just shortening the loop, as opposed to the binary choice of having it/not having it.
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Old 12-03-2020, 18:51   #4
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Re: Vented Loop Question - AWL Head + BWL MSD

If you shorten it, keep in mind that vented loops need to be at least 6-8" above waterline AT MAX HEEL, not just when the boat's at rest. And if you don't need the one between the toilet and the ES, I wouldn't keep it "just to be on the safe side"...'cuz too much of that and you can end up with this! (see photo)

--Peggie
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Old 13-03-2020, 11:34   #5
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Re: Vented Loop Question - AWL Head + BWL MSD

I have a Raritan electric toilet and treatment plant, plumbed with PVC, except a short hose [24"] from pipe to toilet[so i can move], with no siphon break, toilet and plant above the W/L.
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