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Old 13-10-2018, 19:28   #1
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Help needed installing MSD on Thetford 550p

I would be very grateful is anyone could help me with the correct method of installing an MSD with macerator pump on a Thetford 550P

I am building a cat in Indonesia and both I and the local plumber are stumped by the limited documentation that comes with the Thetford 550P with repsct to how to connect the MSD to a macerator pump. I have emailed Thetford and they seem unwilling to offer any advice.

I note that some members have hooked up a macerator pump for overboard discharge to porta pottis - any photos, advice or weblinks would be most welcome.

Many Thanks


Guy Warwick
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Old 13-10-2018, 19:57   #2
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Re: Help needed installing MSD on Thetford 550p

I am very confused... why would you buy a porta-potti and then try to connect it to a macerator pump? Sort of defeats the "porta" part, no? Are you just looking for a cheap toilet?

But if that is what you really want to do, why is it any harder than installing a bulkhead fitting in the "tank" on the bottom and running a hose to the pump? Maybe with a valve in between if that won't break the bank.
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Old 13-10-2018, 20:05   #3
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Re: Help needed installing MSD on Thetford 550p

you are right to be confused - basically getting stuff into INdonesia is a nightmare - corrupt customs asking for bribes and things going missing being but part of the problem - accordingly I hand carried a couple of thetford 550P with Marine Discharge options -
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Old 13-10-2018, 20:18   #4
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Re: Help needed installing MSD on Thetford 550p

I agree that Thetford's documentation leaves a LOT to be desired!



Which version did you buy--the 550P, or the 550P MSD? The MSD version has fittings for a pumpout line and vent line...the 550P (no "MSD" in the model name/#) does not.


If you bought the non-MSD version, you'll have to replace the pour out spout with a PVC pipe that goes to within 1/2" of the bottom of the tank..you'll connect the pumpout line to it. If you only plan to dump the tank at sea, you can install a macerator pump in the pumpout line and route it directly to a thru-hull instead of a deck pumpout fitting. If you also want to be able to pump out the tank, you'll need a y-valve in that that line ahead of the the macerator. You'll also have to install a fitting (or something you can connect a hose to) in the top of the tank for a vent line.



Sounds a bit complicated, but if you're careful and have help from someone who knows what they're doing, it'll work.



Or...you can return the 550P and exchange it for the MSD version. Since the boat is still in the process of being built, it doesn't sound like you'll need it for a while and it'll be very easy to install and plumb once you have the version that's meant to be pumped and or dumped.


--Peggie
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Old 13-10-2018, 20:26   #5
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Re: Help needed installing MSD on Thetford 550p

Many thanks for your reply - I purchased the unit with the MSD Kit - I was truly amazed by Thetford's response "

Iím sorry, we do not provide instructions how to attach our Porta Potti pump out spouts to a pump. "

My guess is that it's some liability issue on the basis of legal advice - makes one wonder what customer service means.

Best

Guy
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Old 13-10-2018, 21:05   #6
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Re: Help needed installing MSD on Thetford 550p

There's no liability issue...You obviously managed to reach someone who's totally clueless if he doesn't know that the pump isn't attached to the pour out spout, but the pour out spout is replaced with the pumpout hose kit and the pump is installed in the pumpout HOSE same as it would be in the discharge hose from any other holding tank.

(And I could have saved myself a LOT of typing if I'd waited for you to reply that you do have the MSD version! Ignore everything I said except how to install the macerator pump.)

Dometic/SeaLand also makes an MSD portapotty--their 975 MSD. The pumpout and vent fittings are similar to the Thetford and they provide a lot more detailed instructions and drawings that should help you sort out how to do it on your Thetford. Dometic 975MSD owner's manual

billknny, an "MSD" version portapotty can make a lot of sense on some boats. The "MSD" designation in the model name/number means it has fittings for a pumpout line and vent line, and is designed to be permanently installed (actually just sturdier brackets than portables, so you could still take it off the boat if you absolutely have to), which means that although it's still called a PORTApotty, you don't have to carry anything off the boat to empty it.

A 5-6 gallon model holds 50-60 flushes...you'd need at least a 30 gal tank to hold that many from a manual marine toilet. No plumbing needed except a vent line and pumpout hose--so no new holes in the boat...and -0- maintenance needed except for rinsing out the tank, which you can do with a bucket while it's being pumped out or dumped. Total cost including the pumpout hose and vent line is about $200--a fraction of what you'd spend for toilet, tank and all the related plumbing needed. And the best part is, you have all the advantages of a toilet and holding tank without giving up a single square foot of storage space.


--Peggie
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