Y-valve below water line ... ok or not ok?

Oct 26, 2008
5,046
Catalina 320 Barnegat, NJ
I am re-plumbing everything connected with the toilet and holding tank with new hoses and a new macerator pump. The current set-up has the toilet discharging directly to the holding tank. The holding tank is emptied either by pump out or macerator pump discharge overboard. There was a plastic T-fitting separating the 1-1/2" hoses that led to the pump or the pump-out deck fitting from the holding tank. If I remember correctly (I've taken it apart already), it was a straight pass thru the T-fitting between the deck cover and the holding tank. The path from the holding tank to the macerator pump had a 90 d bend in the T-fitting, and then another 90 d plastic bend before the hose connected to the pump. The pump discharge is 1" diameter to the thru hole fitting.

So, I'm not really crazy about the T-fitting and I want to replace it with a Y-valve. I want a smoother pass to the macerator pump and I want the ability to close and lock the path to the macerator pump. I empty the tank at sea only when outside the no-discharge zone and the normal position would be closed to the macerator pump when using the pump-out service. I noticed Forespar says their Y-valve is not suitable below water line. I thought I also read that the silicone seal can be damaged by prolonged exposure to sea water.

The Y-valve will be below waterline, but under normal circumstance, the thru hull is closed and the water has to backup past the macerator pump in any case. Typically, the thru hull valve is closed immediately after shutting the macerator pump off. My preferred Y-valve is TruDesign, sold by Raritan, which uses a silicone seal. Since the Y-valve isn't necessarily open to the thru hull, is it ok or would it not be recommended?
 
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Feb 21, 2013
3,916
Hunter 46 Point Richmond, CA
My two cents is 3 way valves are suitable.....I have these in same service on one my powerboat. Moreover, I understand silicone seals in seawater service are acceptable. If in doubt contact Raritan on the acceptability of your application.
 

Dave Groshong

SBO Staff
Staff member
Jan 25, 2007
1,803
Catalina 22 Seattle
A properly installed vented loop is always required, then it is good to go
 
Oct 26, 2008
5,046
Catalina 320 Barnegat, NJ
A properly installed vented loop is always required, then it is good to go
I don't really understand how a vented loop applies to this application. Aside from the fact that the original installation never had it, the discharge thru-hull would only be opened to run the macerator pump. I don't think that I would want to have a vented loop on either side of the macerator pump and there is no place to put one as everything is under a salon bench. Once the pump is shut off, the thru hull must also be shut (otherwise, there would be water backing up into the holding tank). Closing the y-valve on the other side of the macerator pump is a redundancy that I desire (did not have this redundancy originally).
 
Dec 2, 1997
8,168
- - LIttle Rock
Is the discharge fitting on the tank at the bottom of the tank or on the top of the tank with a pickup tube inside the tank? If it's at the bottom of the tank, first thing I'd do is run pvc pipe from the tank fitting to the top of the tank, then switch to hose for rest of that plumbing, using a y-valve to "split" the lines to the tank and macerator pump. Put the macerator pump anywhere you want to between the y-valve and thru-hull...but unless you can find a location for it that's at least as high as the top of the tank (build a shelf for it if necessary...or bolt it to the hull or a bulkhead if you don't have any clearance above the tank) you will need a vented loop in the line between the macerator pump and the the thru-hull if you ever expect to pass an insurance survey.

And there's another reason for mounting the y-valve high: it provides a way to cut off flow to the macerator to replace the impeller or do any other maintenance/repair...'cuz you never discover it needs any when the tank is empty.

--Peggie
 
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Dec 25, 2000
5,103
Hunter Passage 42 Shelter Bay, WA
Our boat has a similar setup as yours except Hunter used a wye fitting rather than a tee. I like the idea of no need to open or close valves when dealing with the sewage operation. Our tank has a stand pipe so when it comes time to empty the holding tank, either the deck pump out fitting is used or the macerator discharge pump. Simple, effective and convenient. No plan nor need to change over the wye fitting to a valve.

The macerator pump through hull valve remains closed until time to discharge the tank contents. Likewise the sea water toilet intake. That valve remains closed at all times until time to flush, so no need for a siphon break. Others might disagree. I suppose there exists some hypothetical where sea water would flow into the toilet and spill over the rim, which is above the waterline, and flood the boat to the point of sinking. Perhaps. Keeping both valves close (intake and discharge) makes that likelihood pretty remote; not impossible. FWIW.
 
Jun 23, 2013
271
Beneteau 373 Newport
Scott, wondering why you want a valve and lock? Concerned with someone operating pump while in no discharge zone? If so, my solution was to wire the pump to a breaker on the panel with a cover over the breaker that has to be raised to turn the breaker on. No switch to operate the pump in the head.
 
Dec 14, 2003
1,324
Hunter 34 Lake of Two Mountains, QC, Can
Newport Bob it's probably because it makes easier to proove to the authorities when boarded for inspection.

While operating in a no-discharge zone, overboard discharge from marine sanitation devices is generally prohibited. To secure a flow-through device (i.e.,. Type I or Type II marine sanitation device), vessel operators must do one of the following:
  • Close the seacock and remove the handle;
  • Padlock the seacock in the closed position;
  • Use a non-releasable wire-tie to hold the seacock in the closed position; or
  • Lock the door to the space enclosing the toilet(s) with a padlock or door handle key lock.
See 33 CFR 159.7(b)-(c) for the relevant statutory language.

All the boarding folks have got to do is look at the Y-valve or locked through-hull to know whether there is possibility for someone to ''inadvertently'' discharge in a no-discharge zone.
Please note that removing the handle on the valve instead of locking or using a wire-tie is also acceptable. In that case however as an inspector told me when I was boarded, the fact that the handle is not there doesn't proove that the valve is shut-off. So he did put the dye in the head and flush while his crewmates checked the water outside. My valve was shut so I was legal thus no problem!
 
Oct 26, 2008
5,046
Catalina 320 Barnegat, NJ
Newport Bob it's probably because it makes easier to proove to the authorities when boarded for inspection.
That's exactly my thinking. I don't even know how to remove the handle to the thru-hull, and I suspect it would be a pia to do so, especially since I will discharge overboard via the macerator pump from time to time when 3 miles out. The previous owner lived with the boat this way for 20 years and never had an issue with authorities, as far as I know. It also seems to me that it is the standard layout for Catalina yachts. No? :huh: But, I will feel more comfortable knowing that any inspection will find the y-valve diverting effluent properly.

The other reason is that the y-valve would provide a means to keep sewage out of the pump when it is not in use. The steps in operation without y-valve go as follows:
  1. Open thru-hull
  2. Empty tank via macerator pump
  3. Switch macerator pump off
  4. Close (as quickly as feasible) thru-hull
If I don't close the thru-hull quickly, I have no idea how much water backs up into and/or past the pump and into the tank.

Operation with y-valve would be as follows:
  1. Un-lock and open y-valve.
  2. Open thru hull
  3. Empty tank via macerator pump
  4. Switch macerator pump off
  5. Close thru hull - as quickly as possible
  6. Close and lock y-valve. (Diverting tank effluent to deck pump-out).
So, in this manner, the only water that would be back-feeding as far as the macerator pump would be sea water (via a 1" diameter discharge hose to the thru-hull), and the macerator pump can be isolated from effluent by closing valves on both sides of the pump. Also, in normal mode, the tank is ready to be emptied via the deck pump out at any time without any opening or closing of valves.

However, because the discharge hose from the tank is at the bottom of the tank, the y-valve would be routinely submerged in effluent (just as the T-fitting always was). I'm thinking this may be the fly in the ointment.

In response to Peggie, the discharge hose from the tank leading to the T-fitting, and ultimately the pump out options, is at the bottom of the tank. The toilet discharge is a 1-1/2" hose directly from the toilet to the top of the holding tank. The tank is under the salon couch and there is no opportunity to install a riser and switch to hose above the tank. All of the current fittings & macerator pump are mounted to the bottom of the hull and are not raised above the tank. I also don't seem to have any room to install the macerator pump at a level above the tank. Right now, and probably for 20 years since the boat was built, the macerator pump has existing on the floor of the hull, with no V-loop between the pump and the thru hull. I don't even see a feasible way to install a V-loop. Insurance survey did not find this to be a problem. I suppose that this is acceptable because the thru-hull MUST be closed at all times, except when discharging overboard at sea.

I think that I am hearing that a y-valve is not a good idea in a location where it will be continuously filled with water or effluent and that a y-valve should always be used in conjunction with a V-loop.
 
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Dec 25, 2000
5,103
Hunter Passage 42 Shelter Bay, WA
Was boarded by the CG last year for an inspection. When it came time to talk about sewage handling, their only question was to confirm that the through hull valve was closed. Handle was still in place, not wired shut or locked, just closed. Maybe different in other jurisdictions.
 
Jun 23, 2013
271
Beneteau 373 Newport
I originally had a y value — chose between pumping from the head to the holding tank or overboard thru the thru hull valve.
I removed the y valve - can only pump to the holding tank.
Emptying the tank is either thru the deck pump out or via the macerater and thru hull valve.
So, someone in head does not have a choice.
Activating the macerater to empty the tank requires opening the thru hull valve in the cabinet under the sink and flipping on the breaker on the panel in the salon (with a cover over the breaker to preclude accidental activation).
 
Dec 2, 1997
8,168
- - LIttle Rock
See 33 CFR 159.7(b)-(c) for the relevant statutory language.
You can read it right here: 33 CFR 159.7 "Requirements for vessel operators."

Types I and II are USCG certified treatment devices...

a Type III is "a device that is designed to prevent the overboard discharge of treated or untreated sewage or any waste derived from sewage." This includes holding tanks, portapotties and "composting" toilets.

You should also find these definitions included in 33 CFR 157.3 informative:
Sewage means human body wastes and the wastes from toilets and other receptacles intended to receive or retain body waste.
Discharge includes, but is not limited to, any spilling, leaking, pouring, pumping, emitting, emptying, or dumping.

---Peggie
 
Oct 26, 2008
5,046
Catalina 320 Barnegat, NJ
Scott, please vist here to see how I completed the very project you are describing
Haro
Yes, that is very similar, except my macerator pump has a short hose between the T-fitting and the pump so I don't have the same problem you did with vibration. Without getting too complicated about my desires, I simply want to replace the plastic T with something that I think is more suitable. Is that 3-way valve a bronze fitting that you got from a marine outfitter or hardware store?
 
Mar 6, 2008
704
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
Yes, it is bronze. I purchased from Groco Model TWV 1500 or three way valve 1 1/2"
I have added more images to the online album to help see the final product.
Let me know if it helped you.
Haro