Domestic Sealand MSD

[rgranger]

Hello

I'm hoping you can help me understand how this works.

I have a Sealand porta pottie that is capable of MSD hook up. The installation instructions are attached and simply show you plumbing the discharge port to a Y-valve that goes to a deck side pump out and/or an overboard discharge. And a plumbing for the vent. I know you have to be 3 miles or so for overboard discharge but I figure if I'm going to go to all of the trouble to plumb it for dock side pump out, I might as well plumb her all the way. The plumbing instructions seem simple enough but...

Here are the issues I don't quite get. The discharge port for the holding tank sits above the tank and exits with a slight incline. See photo....So how does the "stuff" get moving up hill? All of the other diagrams I've ever seen for a marine head have the discharge port on the holding tank exiting the tank at the bottom edge (low point).

1) When they conduct the pump out through the deck plate, do they insert a tube all the way down into the holding tank? If not, how would they be able to suck out the tank if the exit port for the tank sits at the top and not the bottom of the tank?

2) If I ever wanted to or needed to use the overboard discharge, wouldn't I need some way of pumping the holding tank "up hill" to get the "stuff" out of the discharge port? Would I install a mercator, or a hand pump? It just doesn't seem like it would work by simply opening the valve.

In fact the plumbing drawing seems like it would flood my boat if I opened the valve in this configuration. I'd need a loop that went above the water line (yes?)!

Thanks,

r

The photo of the porta pottie is the same unit as mine except I have the 5.5 gallon tank instead of the 3 gallon tank.

 

[jimg]

The dockside pumpout stations I've used are just an air seal, nothing goes down the tube. They would empty a 5 gallon tank in about 20 seconds. If you want to go overboard, yes you will need some sort of pump, manual or electric.

 

[rgranger]

The dockside pumpout stations I've used are just an air seal, nothing goes down the tube. They would empty a 5 gallon tank in about 20 seconds. If you want to go overboard, yes you will need some sort of pump, manual or electric.

Thanks Jim. That is what I figured for the overboard option... but I'm not sure if you understand my question for the dockside.... so I drew a picture on paint. On this porti pottie, both the discharge port and the vent port sit above the "waterline" of the holding tank. What is to keep the air that flows into the tank from just passing over the "stuff" and then out the discharge port to vacuum? I don't see how you can get a "grip" on the "stuff". See photo.

 

[jimg]

Have to ask an expert like Peggy I guess, 'cause I really don't know the physics involved. I would imagine that the suction is great enough to self prime with liquid and then continue on. I do know that is exactly the situation with a regular holding tank: probably some air space on top, and a vent as well. My (smallish) 18 gallon one empties very quickly with no problem like that.

 

[rgranger]

Thanks Jim...

I've never used a pump out station before. All of my boats had porti potties and the few times I chartered we never filled the tank so ...???

I guess it must work .... I'd still like to understand it though.

The reason I'm curious now is I'm about to start on (yet another) restoration of an older sailboat. This time a Rhodes 22 and I'm trying to decide if I want a "real" head or if I want to plumb a porti potty as a "real" head.

I'm leaning towards plumbing the porti potty because I tend to sail in the Pamlico and Albemarle sounds and many of the "marinas" I visit are not much more than a falling down pier. So I can see the need to be able to bring the holding tank ashore for emptying from time to time. The porti potty option provides more flexibility of options.

With this boat, I want to be able to pump out. As it stands we try as best we can not to use the porti for anything more than emergencies because no one wants to empty it out. I'd like to make this boat a bit more comfortable for longer trips. And I have a fantasy of taking it to the Bahamas some day (a few Rhodies on the list serve have made the trip so I'm inspired).

Anyway, thanks for taking the time to help me out.

r

 

[Peggie Hall HeadMistress]

When all else fails, read ALL the instructions

I would imagine that the suction is great enough to self prime with liquid and then continue on. I do know that is exactly the situation with a regular holding tank: probably some air space on top, and a vent as well.

Noooo...that's NOT the situation with a regular holding tank. Contents can only be removed from the bottom of a tank...so ANY tank--water, fuel or waste--that has a discharge fitting on the top MUST have a tube inside it that goes to the bottom...and neither your 18 gallon tank nor this portapotty tank is an exception.

All tanks--water, fuel, waste--MUST also be be vented. The vent has two primary functions: 1. it provides an escape for air displaced by incoming contents...otherwise the tank would pressurize...and 2. it provides a source of air to replace contents as they're pulled out...otherwise, the pumpout (or water pump or fuel pump) would pull a vacuum that would prevent anything from being pulled out. Pumpouts can be strong enough to implode a tank.

The only "air space" at the top is the whatever space in the tank hasn't been filled yet.

The illustration you posted above is only one page in the installation instructions/manual for the 965 MSD...it does not show the complete parts list. That's on page 10... and on that list, you'll see that part #13 is a "dip tube"--a tube inside the tank that goes to the bottom through which the pumpout pulls out the contents. The complete installation/operation manual is here: http://www.scamptrailers.com/Portals/0/Dometic_SaniPottie_960_series.pdf

And btw...it's DOMETIC (no "S")...they're a European company that bought SeaLand Technology several years ago.

Go with a portapotty--portable or MSD, doesn't matter which--on the Rhodes...a "real" toilet and tank would use ALL the available storage space on a 22' boat.

 

[rgranger]

Re: When all else fails, read ALL the instructions

Thanks Peggie

You're awesome.

r

 

[rgranger]

Re: When all else fails, read ALL the instructions

Peggie

Do you have any product recommendations for how I would manually discharge the tank?

r

 

[c_witch]

Hiee,

I installed a new MSD last year on our boat. I still have to add the vent line and discharge lines from the mascerator to the vented loop and aft to the ballcock/thruhull. Maybe this will give you and idea. Our macerator is suppose to have a lift of 5 feet.
Dock side pump outs from what I understand are really nothing more then huge vacume cleaners ie work on sucking the contents out rather then pumping. The macerator I think works somewhat the same way at the start. That is a vacume to pull the contents to the cutter/chopper and then into the impeller at which time the pump becomes primed. Our boat is a 22 footer also. I will be making one change to that shown in the photo's. The first photo shows the macerator adjacent to the msd. I will be installing a stainless steel angle where it now sits so that the pump and be rotated 90 to the left. That will allow the line to the vented loop to exit from the top rather then to the side towards the msd as it now does. The vented loop will be installed above the macerator with the discharge line running thru the port aft bulkhead into the port quarter berth where the seaside ballcock/thruhull are located.

c_witch

 

[rgranger]

C_Witch

Thanks for the photos, especially the labels. It makes a lot more sense to me now. So I need to buy a mercerator, manual pump, a dip tube and some hose (& clamps) and I should be ready to start.

Any chance you still have the model numbers for your mercerator and manual pump?

 

[c_witch]

Hiee,

I'm glad I could be of help to you. NOTE: the manual pump is for pumping out the bilge and has nothing to do with the MSD. I didn't like the idea of only relying upon an electric bilge pump lol, so now we have that one as well as a portable one and a bucket .

Our MSD is a Dometic 974 and came with the parts to make it a sea side pump out. Things you'll need. Deck pump out fitting 1 1/2'' (basically a thru hull type fitting) only the cap seals tightly when not in use. 1/2'' vent fitting ( I am going to change ours over to a simply 1/2'' thru hull and get rid of the current vent fitting. A 'Y' valve, basically a diverter valve with one intake and 'A' or 'B' outlets. One goes to the deck pump out the other to the macerator. I chose an electric pump rather then a manual one. It is a Jabsco macerator and the literature claimed it would lift to a height of 5 feet. You will also need the thru hull fitting(s). I chose to use a thru hull,90 elbow and balcock valve. You will also require the lines 1 1/2'' tank to y-valve, y-valve to dock side fitting, y-valve to pump. The jabsco outlet is 1'' to the vented loop and then 1'' from that to the ballcock. Also be aware that the jabsco draws 16.5 amps so a 20 amp fuse circuit dedicated is required. Oh yeah the vented loop is required lol. In ontario the 'y' valve is required to be locked in the deckside pump out location. When doing the thru hull I used 3M-5200 for sealant inside and out ( very good stuff ). The 974 is the smaller model ie holding tank of only 2.6 gallons. The 975 would have lost another 3'' of head space which is already tight. The 97x series you only fill the flush tank once and then pump up the air pressure ONCE. Simply press a button to flush. If I remember correctly there are 20 to 25 flushes before the water has to be refilled and the air pump redone.

c_witch

 

[rgranger]

Thanks C_Witch

I copied all of that description into a word document and saved it in my project folder. I think I have all I need now.

I have the sealand 965 so it is a manual flush instead of electric but other than that I think all of the specs are the same.

I've been using my 965 in a MacGregor 22 that I own (actually just came back from Ocracoke Island this weekend) and I'm going to start a complete refit of a Rhodes 22 the second week in May. I hope to splash the Rhodes in August or September. The MSD set up will be in the Rhodes so I need to start ordering stuff I'll need now.

I really appreciate your time,

r

 

[c_witch]

Hiee,

Again glad that I could be of help to you. I wish you well in your endeavors for the restoration. It can be somewhat pricey lol. I am now well over budget on mine. If you need any assistance later on feel free to drop a private message or post here. I usually check the trailer sailor section daily and the ask all sailor section at least every other day and usually here as well but not always.

Ours is not an electric flush btw. Pushing the button just releases a predetermined amount of water into the bowl jets via air pressure hence having to pump up air pressure when the water tank is filled. We are cruisers and not really interested in racing. I have tried to set our boat up for extended cruising. With the addition of the 20 gallon fresh water tank this spring I am thinking that we would be good for a 9 to 10 day passage on the open water perhaps longer if we can conjure up some type of water capture system for rain water to refill the tank.

Our boat is a Yankee Condor. There where very few of them built and virtually no information about them anywhere.

c_witch

 

[rgranger]

I wish you well in your endeavors for the restoration. It can be somewhat pricey lol. I am now well over budget on mine.

Ha ha.... Yes!

This will be the 5th boat I've restored. I find them very cheap, fix them up, sail them a few seasons and sell them. I got the Rhodes for $250. Some kid got it for a graduation present, sailed if for the summer and then abandoned it at the slip with the hatch open to the rain. The marina finally took possession and they were a power boat place so, they just wanted it gone.

Oh yeah, the kid purchased a brand new main sail :dance: I might need a new head sail, I haven't inspected it yet... it is still rolled up on the furler.

So I have some carpentry work ahead of me, and I'll replace all of the standing rigging, ports and rebed all of the deck hardware, then a bottom job and I should be done.

The MacGregor I'm now sailing cost me $850 and came with a trailer and 5 sails. However I'm not sure I'm going to be able to part with my Mac this time. She really sails well. I'll get 6kth out of her in a 9kth wind with no problems.

I'd like to set up the Rhodes with the thought of extended cruises and keep the Mac for short weekend trips.

Fair winds,

r

 

[Peggie Hall HeadMistress]

Keep it simple...don't over complicate it!

Peggie Do you have any product recommendations for how I would manually discharge the tank? r

You do NOT need to buy a diptube...or anything else that's shown on the exploded drawing/parts list for your potty. You DO need a y-valve and EITHER a macerator pump or a manual diaphragm pump (I have no idea why c-witch installed both)--a vented loop and some hose. Break the pumpout hose...install the y-valve. One side of the y-valve the deck pumpout, the other side to the pump...out of the pump and over the vented loop to the the thru-hull. That's all there is to it. Use Trident 101 for your 1" and 1.5" hose...Shields or Trident #148 is ok for your tank vent.

I'd go with Whale y-valve (avoid Jabsco, they leak)...Be sure to put the y-valve and pump in a readily accessible location.

c-witch...I can't figure out your plumbing from your photographs...Surely you didn't install both a manual diaphragm pump and a macerator pump to dump the tank at sea???

The macerator I think works somewhat the same way at the start. That is a vacume to pull the contents to the cutter/chopper and then into the impeller at which time the pump becomes primed.

Nooo....there is no vacuum. Macerator pumps are impeller pumps. Impellers IMPEL (pull)--hence the name "impeller"--liquid through the pump using centrifugal force...the macerator/chopper blade is actually AHEAD of the impeller so that it can puree anything that needs pureeing to get through the impeller... I suggest you read the instructions, including the exploded drawing that shows how it works, which you'll find here: http://www.xylemflowcontrol.com/files/itemdoc1201.pdf

When doing the thru hull I used 3M-5200 for sealant inside and out ( very good stuff )

You'll live to regret that! 5200 is the most mis-used product on the planet...it really has no place on boat 'cuz it's not a sealant, or bedding compound... it more closely resembles super glue. It hardens, when means it cracks instead of stretching and contracting with temperature and flex. It IS permanent...but that doesn't mean it'll never leak. And when it does, you'll play hell removing it to replace it with the bedding compound or silcone sealant you should have used in the first place.

And you don't want to install a stainless steel--or any other metal--ANYthing in a line that carries sewage...urine is so corrosive that it'll destroy it in a season or two. Use PVC instead.

 

[LloydB]

c-witch caught up the manual diaphragm pump pic with the Note in reply #11

 

[c_witch]

Hiee Peggie,

I have not used the 3M 5200 marine before;however, it was recommended to me by my supplier and the literature I read seemed to support his claims.


3M™ Marine 5200 Adhesive Sealant

High-performance polyurethane adhesive sealant that stays flexible and waterproof, yet resists weathering and salt water. Bonds and seals woods and fiberglass of boat hulls.


I am familiar with how pumps work. And I do know that with a macerator the cutter is in front of the impeller to chop solids into paticulate. Being as these pumps Don't have a foot valve on them ie the bottom of the pick up tube it seemed logical to assume that they must create a minor vacume in order to pull the liquid to the impeller at which time the impeller would take over and push the liquid thru the remaining system? Failing that would they not need to be primed each time, and how would one prime them without there being a foot valve?


The stainless was simply so that I could reorientate the macerator so that the output was facing upward rather then towards the MSD ie making it easier to make the hose connections to the vented loop. Perhaps an aluminum angle would be a better choice. I worry about plastic due to the vibration from the pump causing fatigue cracking at the bend.


c_witch

 

[njwtech]

you don't want to install a stainless steel--or any other metal--ANYthing in a line that carries sewage...urine is so corrosive that it'll destroy it in a season or two. Use PVC instead.

What do you recommend for the pumpout fitting on deck then? I don't want anything made out of PVC that people will be walking on and the only logical place for a pumpout fitting on my boat is bedded right in the middle of the side deck... Thanks for sharing your expertise.