why groco why

[markxengineerin]

I have the esteemed Groco model K head, circa 1994, and have unsuccessfully rebuilt it. It is still recirculating. This next attempt, I'm going to hone the cylinder (it is pretty scored up) and possibly change the piston rings to "x rings", which are like o rings but used in reciprocating applications. Shaped like and X so they don't spin around and rip. Getting the rings past the open "port window" will be a little tricky, but I think do-able.

To those who have rebuilt marine heads, can you describe the piston rings? Are they all plastic/delrin like the Groco or have other materials been used? Do they usually require some amount of user adjustment, or just fit?

Here are my complaints about the Model K, omitting some questionable fastener locations which are more of an inconvenience.



Location 1: piston rings that need to be peened with a hammer until they become a tight fit in the cylinder. There is no chance deforming a piece of plastic in this way is going to create a perfect fit. Why not supply oversized piston rings, not undersized, and simply file the ends to fit, like every other piston ring in the world?

Location 2: Paper thin wall between fresh water to the bowl and the contents of the bowl. So easy to make this a reasonable size and not risk a leak.

Location 3: Sealing surface left rough as cast. Mine sprays pressurized water out of this interface when pumped hard, easily preventable by machining it flat. Also, the thickness of this part influences the sealing of location 2. The rubber bowl gasket is thick enough to tolerate a lot of variation here, but just doesn't make any sense why they'd not correct this on a $1200 toliet after decades in production.

[mvweebles]

I bought a Model K new at about the same time - 1994. I just sold it and replaced with a Nature's Head.

I rebuilt it a few times over the 25-years I owned it. I never had any of the problems you're talking about. Never peened the rings - just instaled them. Only challenge was getting the piston connecting rod re-connected.

As far as Location 3, there is a thin O-Ring around the 3-inch circumference of the plate. Not sure if that's where you're seeing spray.

I normally used 3M 4000 to seal the main gasket.

Honestly the only issues I had with the head is the tiny bronze spring that holds the flapper in place eventually breaks after 5-years or so. Some of the shaft seals eventually leak too. Not sure what you plan to replace it with, but hard to believe it will be an improvement unless you go with a higher quality freshwater head such as a Raritan Marine Elegance.

[markxengineerin]

The spray at location 3 isn't from the o ring, which seals ok, it's the flapper to bronze interface.

The coat hanger mentioned in the manual worked for me on the piston connecting rod, but yea, could be more user friendly there too. I have also broken a spring.

I'm surprised you didn't get any recirculation with the rings installed "as-is", since the manual mentions the peening. As far as I can tell, there are no other possible parts to blame, and mine is recirculating badly after installing without peening. I thought peening sounded like a bad idea and the fit seemed decent without it. The amount of recirculation makes me think it must be some other cause, but looking at the parts/design, I can't imagine what. It's a big problem because I have a small holding tank, so extra pumps are not helpful.

I don't want to replace, I like the heavy bronze and age of it, just want to upgrade the piston rings to something less finicky.

[mvweebles]

At one point mine recirculated too. I think it was the 3/4" black rubber ball. There is a bronze bolt (#8??) That retains it from. Moving. Honestly, I forget exactly but if I remember correctly, recirculation is related to that.

Pretty sure the casting has not changed on 35 years. These are now very expensive heads. I doubt Groco sells more than a couple each year.

[peghall]

I have the esteemed Groco model K head, circa 1994, and have unsuccessfully rebuilt it. It is still recirculating.

That unfortunately is what Groco Model K toilets start to do after about 20 years.

This from Groco:

"The K type heads begin to recirculate black water when the piston bore wears beyond spec and the rings allow pressure to blow by. Furthermore the piston is double action pumping black water on the up stroke and raw water to the bowl on the down stroke. You can replace the bore housing but that would be more expensive than replacing the heads completely with another well known brand.

"The rebuild kit will not solve this problem but you can do a couple of things to pump a little more life out of an old K-head.

Take a new set of nylon rings and pound them between two flat pieces of hardwood to increase their diameter and install them with the heaviest grease you can find. This will stop the blow by until the rings wear down.

"If you are handy you can also hone the bronze bore and turn yourself an oversize nylon piston."


f you want to discuss it with Groco you can call them:

410-2499-4030

or email them:
info@groco.net


-Peggie

[gonesail]

i inherited a groco HF. it was not pumping right. i ordered an entire new pump assembly. amazing prices but it works

[SailingHarmonie]

What I think is really funny is that we have the original pair of Jabsco manual toilets that were installed on our boat 27 years ago.

They require some maintenance (like all boat systems), but I am 100% sure that we have not spent--in aggregate--the dollars that a groco would have cost to just to install in the first place. Yet, somehow, the Jabsco's get no respect. For us they just work. 7 days a week, 365 days a year. Year after year...

[mvweebles]

Also, if the underside of the plate that the flapper mounts to is rough, take a sander with 220 to it. Nothing sacred.

[markxengineerin]

The ball looks like it would be pushed up to unseat by flow of fresh water to the rim of the bowl, when the piston travels "down", making pressure in the fresh water reservoir area.
Then, when pressure is removed, it would sink and stop any water above the ball from draining back down into the fresh water reservoir area, or maybe flow in the other direction, if that's the concern depending on where the waterline is.

I can't think of why this is a necessary feature (maybe to save a bit of time by keeping air out of the circuit? But how does any air get in?) or how it could influence recirculation, but maybe I am not understanding it right. I wish this to be the case, this would be an easier problem to solve, and more believable.

[markxengineerin]

@peggy thanks for the tip on the 2 pieces of wood- that sounds a little better than hitting individual places with a hammer. Still don't understand why not use conventional piston ring technology..

[markxengineerin]

The ball in question does sink, but it has a seam + a sprue hole type discontinuity that could prevent a seal unless it was under a lot more pressure than the head of water above it is likely to provide. This makes sense, as my bowl does fill up slowly with a small amount of clean water after I have emptied it. A check ball should be round!


Edit: I think I understand now, this ball would be under some pressure when the piston is traveling "up", which makes a vacuum in the fresh water reservoir area. This ball prevents air from being sucked in from the rim, and instead the reservoir pulls replacement water in from the seacock. Nothing to do with recirculation, though, that I can see.

[Bowdrie]

I've forgotten who it was, but someone in the past posted that they had replaced the factory piston rings with a particular size/type of O-ring and then the toilet worked fine.
With a bit of luck maybe they'll chime in.

[peghall]

Are you sure they aren't like several generations of a family who'd inherited George Washington's axe...3 heads and 4 handles later, it's still George's' axe...or in your case it would be 6 pumps, 4 bowl gaskets,and 6 joker valves and 3 wet/dry cam assemblies later ithey're still your 27 yr old toilets ???


--Peggie

[peghall]

Call Groco, Mark That piece from Groco that I posted has been in my files for quite a while...they may may have updated solutions now. It won't cost you anything to find out.


-Peggie

[markxengineerin]

Yes, will do, I tried today prior to posting but just missed business hours.