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Old 06-05-2015, 14:55   #1
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Rebuild question on Groco K

I've disassembled the head and the piston (12) has NO O-ring grooves such as is shown on the exploded view of the head (attached). Do I have such an old piston that they didn't have a groove or is there no groove that the piston rings set (46) fit into (I can't imagine that's the case??).

It doesn't seem it would work very well without a seal around the piston. I.E. black water could move past the piston into the sea water intake side.
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Old 06-05-2015, 16:07   #2
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re: Rebuild question on Groco K

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Originally Posted by Redduke View Post
I've disassembled the head and the piston (12) has NO O-ring grooves such as is shown on the exploded view of the head (attached). Do I have such an old piston that they didn't have a groove or is there no groove that the piston rings set (46) fit into (I can't imagine that's the case??).

It doesn't seem it would work very well without a seal around the piston. I.E. black water could move past the piston into the sea water intake side.
Yup...that is what can happen...and I hear from a lot of Model K about it, 'cuz Model K toilets are very prone to start recirculating after about 15 years (more or less, depending on how much use they get...obviously sooner on liveaboards than on weekend warrior's boats)...rebuilding and replacing a couple of parts should cure the problem unless it's allowed to happen without maintenance for too long. Give Groco a call...they'll be able to help you with the parts and advice you need. 410-604-3800
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Old 08-05-2015, 05:36   #3
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re: Rebuild question on Groco K

Thank-you

I'll give them a call.
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Old 08-05-2015, 07:51   #4
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re: Rebuild question on Groco K

OK, so I called Groco and he said that this is an old model, mid 1970's and earlier. The piston skirts are almost twice as long as the later "ringed" version so the piston has less of a chance to jam up with paper. The newer short ones will rotate a bit and jam against the side of the wall when paper gets in them. He said it is actually better performing and does not need rebuilds as often.

The reason for the change to the ring version was to reduce water consumption as holding tanks were installed on boats with restrictions in overboard discharge. With my older version if there was some mixing, you just kept pumping till cleared.

The piston to wall gap is very small in mine so he suggested I just pack with grease.

I just thought I'd follow up here for future reference.
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Old 29-03-2016, 05:43   #5
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Fix recirculating problem on Groco K Head?

Quote:
Originally Posted by peghall View Post
Model K toilets are very prone to start recirculating after about 15 years (more or less, depending on how much use they get...obviously sooner on liveaboards than on weekend warrior's boats)...rebuilding and replacing a couple of parts should cure the problem unless it's allowed to happen without maintenance for too long. Give Groco a call...they'll be able to help you with the parts and advice you need. 410-604-3800
Hi Peggy (and anyone else ),
Do you know which parts specifically lead to the recirculating problem?

I called Groco and they said it's likely the head is just "worn out" and suggested an entire replacement. No can do. Apparently. (See below.)

We are currently cruising and stopped in La Paz, Mexico. We rebuilt the head in 2013, and in 2015, less than 6 months ago and it worked okay until recently. Now it works more like a blender than a head - with little chunks of sh...errr...solids mixing with intake water and coming back out of the bowl flush openings. Removing all the waste from the bowl takes many pumps and a lot of seawater. Which is not a huge problem when we are at sea and can empty the holding tank when needed, but a real headache when anchored or in a marina. Plus the smell.... crap.

The head is likely original to the boat - or 28 years old, although you wouldn't know by looking at it. Everything about it is clean and in great shape, except possibly the 'new' internal parts or base - which are causing the recirculating problem - which we haven't been able to identify with the naked eye. We have a rebuild kit onboard. Or, should /could part of the base be re-machined?

And, if we can't fix it, where should we go in La Paz to order a new head? The very-fluent-in-English sales guy at Lopez Marine said yesterday, "There is a ban on ceramics coming into Mexico, so I can't order you a new toilet." And then went on to explain how he ordered some ceramic coffee mugs and "they" wanted a $300 peso import fee for each mug. BS? I wonder what Home Depot is doing....selling wood outhouses?

Or, should we order a new head from a stateside supplier and have it shipped here? And how does that even work?

Thanks much for your advice everyone. We really appreciate it.
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Old 29-03-2016, 11:51   #6
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Re: Fix recirculating problem on Groco K Head?

Unfortunately EVERYTHING, even a bronze toilet pump, has a lifespan...The piston and the pump cylinder wall become so worn and out-of-round that that they allow bowl contents to recirculate, which is exactly what yours is doing.

But there is an affordable solution: you can replace just the "piston crank assembly" (part # K32) with the new version that has the grooves and seals. It won't last another 30 years, but should give you at least 5-6 years more. Price direct from Groco is very reasonable and if you've been able to rebuild the toilet once, it shouldn't be a difficult job. Patrick at Groco will be glad to walk you through it.
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Old 29-03-2016, 12:08   #7
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Re: Fix recirculating problem on Groco K Head?

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you can replace just the "piston crank assembly" (part # K32) with the new version that has the grooves and seals. It won't last another 30 years, but should give you at least 5-6 years more. Price direct from Groco is very reasonable and if you've been able to rebuild the toilet once, it shouldn't be a difficult job. Patrick at Groco will be glad to walk you through it.
Hi Peg-
Thanks so much for the reply.

Unfortunately, our head already has the piston with grooves and rings. Yes, rebuilding it (twice now) wasn't difficult. But we don't want to have to rebuild it every six months at $100 a pop.

May be time for a new one. Dang. Since the bowl, lid and handle are in perfect condition, maybe we should just order the base. But Groco said they are as much as a whole new toilet. But, that might make it easier to get the part into Mexico. It's a lot smaller at least.

If total replacement is the only option, would you go with a Raritan Marine Elegance w/seawater option, or replace the Groco base. Footprint space, wiring, and installation won't be a problem.

Getting a whole toilet in /into Mexico may be.

Thanks again.
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Old 29-03-2016, 15:16   #8
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Re: Fix recirculating problem on Groco K Head?

Welll...so much for Plan A.
Moving on to Plan B...The Marine Elegance with the "Sea Fresh" option would be my first choice, but not if the "penalty" for importing ceramics is as bad as your La Paz boat store guy says it is. If so, replacing the Groco pump and base is only other choice that makes sense....although if it's gonna cost you as much as the Elegance + shipping and ceramics fee, go with the Elegance anyway.

Plan C: send your pump back to Groco...Patrick will restore it to factory specs. Buy the cheapest solution you can live with--even a portapotty--to use till you get it back.
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Old 03-04-2016, 10:36   #9
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Re: Rebuild question on Groco K

We decided to disassemble the head and take another look before we ordered anything. Groco said the rings should fit "tight". Well, how "tight" is right?

So we asked Groco for the specs of a new base so we could see if and/or how far out of spec our old head really was.

New Groco Model K Factory Specs are:
Piston diameter: 2.928
With rings on: 2.999
Bore (cylinder inside diameter): 2.999 - 3.000 +/-.005

Since we did an entire rebuild 6 months ago, we were able to disassemble, clean, and reassemble the base using the same parts, saving our spares kit for later. (The spares kit costs around $100 in the US, but is $2,505 pesos at Lopez Marine in La Paz, Mexico - which is $144 at today's exchange rate of $17.34.)

The rebuild procedure calls for flattening out the rings to enlarge/expand them by tapping them gently with a hammer, which we did. And now the rings fit "really tight" inside the cylinder. We used regular Vaseline as a lubricant.

And the problem is solved. No backwash or recirculating of waste. It was very helpful to have the specific specs. Thanks, Pat!
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Old 03-04-2016, 10:37   #10
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Re: Rebuild question on Groco K

And thanks to Peg Hall also!
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Old 03-04-2016, 13:15   #11
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Re: Rebuild question on Groco K

Good job! I'm gonna save your post to my files, 'cuz Groco Ks have always been popular on trawlers, and at almost every rendezvous where I'm invited to conduct seminars I run into older ones that recirculate.

However, next time you lube the piston rings, use silicone or teflon grease, 'cuz Vaseline is a petroleum product and petroleum is destructive to rubber and nitrile. Your one application won't do any noticeable damage, but if you don't want to have to replace the rings again, avoid using Vaseline in the future.
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Old 04-04-2016, 09:33   #12
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Re: Rebuild question on Groco K

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However, next time you lube the piston rings, use silicone or teflon grease, 'cuz Vaseline is a petroleum product and petroleum is destructive to rubber and nitrile. Your one application won't do any noticeable damage, but if you don't want to have to replace the rings again, avoid using Vaseline in the future.
According to Patrick at Groco, the white plastic piston rings for the Groco K are made out of an acetal resin called Delrin - which, according to Dupont (the company that makes it) is resistant to a whole list of chemicals including diesel fuel, gasoline, oil, etc. (See page 23 on the attached doc if you're interested. LOL) Delrin is also resistant to urea and vinegar, which makes it the perfect choice for a marine head piston rings. So, Vaseline won't degrade the rings in the least bit.

Nitrile is used in the automotive and aeronautical industry to make fuel and oil handling hoses, seals, grommets, etc since ordinary rubber cannot be used. Mechanics use nitrile gloves to protect their hands from petroleum products. We have a box on board.

The Groco instructions call for Marine Grease when rebuilding the head. Marine grease is petroleum based, with other stuff added so it holds up really well in the marine environment.

Laughing out loud now...I never thought I'd spend this much time or effort figuring out how our head works.

Hope this info is helpful to other Groco head owners.

Cheers, mates.
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Old 04-04-2016, 13:46   #13
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Re: Rebuild question on Groco K

Aha...the rings are plastic, not rubber or nitrile. I learn something new almost every time I log onto a forum.
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Old 05-04-2016, 10:20   #14
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Re: Rebuild question on Groco K

As do we. Thanks again for your help, Peg! We really appreciate it! Your vinegar tip is spot on. It was amazing how quickly it dissolved the salt accumulation on the internal parts.

By the way, flattening out the piston rings so they fit really, really tight against the cylinder (see post above) has completely solved the problem of recirculating poo. The head works likes new and the holding tank odor is no longer seeping past the rings.
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Old 11-04-2016, 07:12   #15
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Re: Rebuild question on Groco K

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We decided to disassemble the head and take another look before we ordered anything. Groco said the rings should fit "tight". Well, how "tight" is right?

The rebuild procedure calls for flattening out the rings to enlarge/expand them by tapping them gently with a hammer, which we did. And now the rings fit "really tight" inside the cylinder.
When I rebuilt my Groco K toilet last year, I saw the instructions to flatten the piston rings with a hammer. I looked at the plastic rings, then I looked at the hammer, then I chickened out. Surely, I thought, the instructions must refer to an older metal ring... no way am I going to hit this little piece of plastic with this big steel hammer. Well, I now have a recirculating toilet.

Tell me, what am I changing when I flatten the piston rings? Am I making the ring wider, that is increasing the width of the ring thus making the outside diameter greater and the inside diameter smaller? Or, am I making the piston ring longer so that the gap disappears thus making the piston ring bigger in diameter?

Do you have any pointers or technique? I think a re-rebuild is in my future.
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