New skin fitting

[clonlara]

My new to me boat is fitted with a holding tank but no way of pumping waste overboard when offshore. I therefore want to fit a new skin fitting with a diverter valve. What diameter skin fitting is recommended and also which valve type would the forum recommend. Thanks

 

[sailorman]

what toilet do you have

 

[macd]

clonlara: 38mm is generally used for toilet outlet. Material: DZR brass, bronze or Marelon (plastic), but not plain brass, with ball valve of complimentary material in each case.
The more usual system would, however, be for the holding tank and direct loo outlet to share a discharge skin fitting, although perhaps this is difficult to arrange in your case.
Are you saying that the only way of emptying the tank at present is via a deck pump-out?
Is the bottom of the holding tank above or below sea level?
It would help if you could describe the layout of the existing piping from the loo and to the holding tank.

 

[clonlara]

The toilet in question is the RM 69 which discharges directly into the holding tank which is factory moulded in under one of the bunks. Essentially they have taken one of the storage compartments and made it into a holding tank. Thanks for the replies so far.

 

[macd]

Thanks, clonlara.
So the waste in the holding tank can exit where?
And if it's under a bunk does that make it partially below seawater level?
I presume there's no way to access the interior of the holding tank?

 

[clonlara]

The waste can only be disposed of via a discharge pump in a marina. It is fully below sea level. The only way to access the interior is through a large fibreglass hatch which is sealed with a sikaflex type sealant by the previous owner . This is also screwed down. It is however impossible to open as the cover sits in the rebated opening which would ordinarily be used for a locker cover

 

[macd]

Got it, thanks. Sounds a bit daft, but clearly not your doing.
So...and excuse any earlier thickness on my part...you want to discharge the loo into a 'T' or 'Y' valve, then to existing tank or sea. Should be pretty simple.

There are several choices of such valves. E.g. see here: http://www.force4.co.uk/department/chandlery-below-deck/plumbing/diverter-valves.html
RM 69 toilet outlet is 38mm, so valve will be the same (as will the skin fitting valve). I've used both types of 38mm/1.5in valves on that link. The cheap ones weeped a little (fortunately only with fresh water in my case); the Whale valves are well-made (although I'd prefer to see a ridged barb rather than the smooth one employed). There are other choices of valves, but cheap definitely is not cheerful with this application. Where barb length permits, double clip the hoses at all points. Clips should be all-stainless, including the screw (handy having a magnet to check).

Try to engineer it with the hose runs as short and straight as possible, although obviously tank and loo are fixed points. Use good quality sanitary hose, which will help preclude pongs (as will a fairly large-bore holding tank breather, although that may be difficult to arrange).

It might be worth trying to find someone who's had the same issue on a similar boat: your specific arrangement isn't something I've tackled myself.

There's plenty of info on line about general arrangement of such a system, both via Google and on sites such as Jabsco's.

 

[vyv_cox]

Have the builders used other parts of the RM69 toilet assembly? Their wrap-around holding tank is emptied by switching the spectacle blind on the back of the toilet, then using the toilet's pump to empty the tank. Arrangement shown here http://www.rm69.nl/buffertank/

 

[prv]

Use good quality sanitary hose

Very important - and I'd recommend this stuff: http://www.asap-supplies.com/marine...water-hose/seaflow-butyl-sanitation-hose-38mm . As well as being impervious to smell, it's also much more flexible and easy to work with than the traditional stiff white plastic hose. This might be important in a retro-fit installation like yours where some of the corners and joints might be a bit cramped.

Pete

 

[BabaYaga]

The waste can only be disposed of via a discharge pump in a marina. It is fully below sea level. The only way to access the interior is through a large fibreglass hatch which is sealed with a sikaflex type sealant by the previous owner . This is also screwed down. It is however impossible to open as the cover sits in the rebated opening which would ordinarily be used for a locker cover

As the holding tank is below sea level, you will need a pump (electrical or manual) to be able to discharge the tank contents to sea.
Is the discharge fitting on the tank situated in a low spot? (suppose so if it's under a bunk). Then put a 38mm T-fitting in the discharge hose at the lowest point possible, take the new hose to the discharge pump and from there to the sea cock (hose tail+ball valve+skin fitting).
This basic set up would allow you to choose between discharging through the deck fitting (marina pump out) or to sea (by the discharge pump).
You also might consider one or two extra valves in the 38mm pipe work.
My s/s tank is also under a bunk, seen in the top of this picture. The hose leading to the deck fitting is to the left. Skin fitting is bottom right. The hose seen along the right edge leads from toilet to tank.
http://www.ybw.com/forums/images/attach/jpg.gif
Note that with this set up you will still not be able to pump out to sea without going through the holding tank. To get around this is not impossible, but involves more hardware (I have another T-junction/seacock between toilet and tank, not visible in this photo).

Regarding size of valve, skin fitting etc: 38mm = 1 1/2", but IMHO you can get away with 1 1/4" if you use metal parts, like DZR brass. This is based on the ID of hose tails etc, which will typically be something like 32-33mm.

 

[KevB]

I'm just going through the process of replacing my skin fittings and seacocks on my holding tank, the discharge on mine is only 25mm and has worked fine for the last 13 years although the pump is also a macerator.

This looks great value http://www.ebay.co.uk/itm/12V-Macerator-Water-Waste-Pump-for-Yacht-RV-Caravan-Trailer-Camper-Marine-Boat-/381044638663?pt=UK_CarsParts_Vehicles_BoatEquipment_Accessories_SM&hash=item58b807c3c7

I have the same brand pump for my domestic water and it works very well.

 

[Fendant]

Well I think that "bigger is better" is especially true for the toilet outlet, although 1 1/4( which I have ) seems to wokr I would go for 1 /2 fo een 2" for the skin fitting. I would use "true design " reinforced polyamide fittings and valve from Australia and connect them via the best flexible sanitary hose o can buy to the loo. I assume that the loo is above the waterline and your strange holding tank ( smell ?? ) is below. Then you an use a valve to channel the waste fluid either / or

If your loo is below WL then it get as a previous poster said more complicated. Do you still Need or will you need in the near future a holding tank in your area ?

 

[clonlara]

Hi guys thanks for all the help so far. Just a little bit of background on the boat. It is a Canadian built Sirius 28 built around the early eighties and was brought over to Ireland in the late eighties by a guy who was coming back to live. It was lying unused for a few years until I bought it this time last year initially as a bit of a project but I soon came to appreciate its build qualities and so sold my existing boat. As I had not seen it in the water before I bought it a.nd had little references to go on some issues only came to light during the first season of use and I am trying to address these before she goes back in in March. The Toilet discharges directly into the holding tank high up in the tank. This can only be emptied by use of a suction hose at a discharge station. the tank itself is I have previously said part of the internal moulding. There is no smell in the cabin as it is very well sealed, but I am worried about water sitting permanently on the inside of the hull and it just doesn't seem best practice hence the modifications.

 

[vyv_cox]

After your clarification, many holding tanks, including mine, are gravity emptied without a pump or diverter valve. The only drawback is that there is no option, everything either goes straight through or is retained by the seacock. Despite this, I believe it is preferable to diverter valves and other complications, which are not very reliable. A 1.5 inch connection has been pretty much standard but I have seen 2 inch offered recently to help avoid blockages. You need a vent of course but you probably already have one.

 

[charles_reed]

The toilet in question is the RM 69 which discharges directly into the holding tank which is factory moulded in under one of the bunks. Essentially they have taken one of the storage compartments and made it into a holding tank. Thanks for the replies so far.

Raske & Van der Meyde actually produce a diverter valve for their saddle-tank, this allows you to either discharge into the tank or to the sea through the normal outlet and to pump out the contents of their tank into the sea.
It does need to have the inlet pipe into the holding tank, going to the very bottom.
I've always dealt with them direct, but they prefer if you go through their distributors, because they have no CC facilities - so involve invoice and bank transfer. Look here:-
www.rm69.nl/

PS Always found them very good to deal with - even when it's down to faulty product and their UK agent just hid his head...

 

[BabaYaga]

After your clarification, many holding tanks, including mine, are gravity emptied without a pump or diverter valve. The only drawback is that there is no option, everything either goes straight through or is retained by the seacock. Despite this, I believe it is preferable to diverter valves and other complications, which are not very reliable. A 1.5 inch connection has been pretty much standard but I have seen 2 inch offered recently to help avoid blockages. You need a vent of course but you probably already have one.

The tank is fully below the water level (see post #6) so cannot be emptied by gravity.

To the OP: Is there a deck fitting for pump out? If not, where would the suction hose of the discharge station be attached for pump out?

 

[vyv_cox]

The tank is fully below the water level (see post #6) so cannot be emptied by gravity.

To the OP: Is there a deck fitting for pump out? If not, where would the suction hose of the discharge station be attached for pump out?

I may have misunderstood what he said - 'discharges high up in the tank'.

 

[clonlara]

The tank is fully below water level and yes there is a deck fitting for pump out similar to a diesel fill fitting

 

[BabaYaga]

The tank is fully below water level and yes there is a deck fitting for pump out similar to a diesel fill fitting

I think you must first decide if always pumping to the tank is OK, or if you want the possibility to discharge directly from toilet to sea.

Next question is if the toilet pump can be used to empty the tank (can it efficiently pump air)? Mine can't, but this may vary. Size of tank will also be a consideration here, I think.

If the answer is no, you need a separate discharge pump as per my post #10. In this scenario I am not sure what a "diverter valve" really does. It is more a question of whether you accept the tank content standing in the hoses or if you want to minimize this. (I assume here that the discharge hose attaches to the bottom of the tank. If it is by a dip tube this is less of an issue).

PS. using the toilet pump for emptying the tank also requires a valve in the vent hose. Wouldn't recommend this.

 

[KevB]

The tank is fully below water level and yes there is a deck fitting for pump out similar to a diesel fill fitting

I see it that it has to be diverter valve to self priming macerator pump to seacock and skin fitting.