Hard pumping head

Dave Spencer · June 21, 2017, 10:36:36 AM

Quote from: KWKloeber on June 21, 2017, 07:14:11 AM
Quote from: Jeff Kaplan on June 21, 2017, 06:11:12 AM
it was the pump stroke that was hard, all fixed now, I never should have installed an in line strainer.

Strange, I don't see how a blockage on the inlet side would cause hard pumping on the pump stroke. Seems it would cause a vacuum when pumping on the intake stroke.

k

Jeff's answer makes sense to me Ken. When pressing down on the pump handle, waste is being discharged from the pump to the tank on the piston side of the cylinder while fresh water is being drawn into the pump on the rod side of the cylinder. Any restriction drawing in water like the clogged filter Jeff described would certainly cause a hard pumping head.
The upward stroke (or intake stroke as you called it) pumps water from the rod side of the pump cylinder into the bowl while the piston side of the pump draws waste from the bowl into the pump.

KWKloeber · June 21, 2017, 03:01:42 PM

Dave

My 30 has a Groco head w/HF series pump - have no idea what you guys have. It's been many years since I had the pump apart to replace any guts, and the last time I simply replace the entire pump. But as far as I remember there is no water on the rod side of the plunger.

The intake stroke and outlet stroke to the bowl is controlled by basically check valve. The seal at the top of the pump for the rod is basically just a tiny seal that would not hold any pressure, it's just meant to not let any blowby out. By blowby I mean blowby past the main cylinder plunger seal.

IIRC (it's been many years and CRS) that seal on the plunger is like a leather cup seal on an old hand well pump, that is, a cup meant to seal primarily against pressure on one side (water in the cylinder on the underneath side the seal in our case.)

As far as I can remember the pump is single action, not double action. i e., on one stroke water fills the cylinder below the main seal, on the next down stroke it pushes that water out to the bowl. Or if the lever is flipped, the upstroke pulls poopie from the bowl to the cylinder, and the down stroke pushes it out to the tank through the joker valve.

Am I miscorrectly misremembering the guts of the pump, or are your guys' pumps different? i.e. double-action plungers?

Dave Spencer · June 21, 2017, 03:42:12 PM

Jabscos are double acting. Sadly, I've had mine apart several times. Good video explanation here:

https://youtu.be/BnQq4d-NmkE

KWKloeber · June 21, 2017, 04:46:52 PM

Quote from: Dave Spencer on June 21, 2017, 03:42:12 PM
Jabscos are double acting. Sadly, I've had mine apart several times. Good video explanation here:

https://youtu.be/BnQq4d-NmkE

Well, there yah go. Another day, another "learn something new."

Thanks Dave!

Jeff Kaplan · June 22, 2017, 11:27:43 AM

Guys, what I found out was in the Jabsco, that on the pull up, the waste was being removed, the down stroke brought in sea water. As the strainer was on the down push, that's where the pressure was. As stated, removal of the inline solved the problem, pumping like a champ now.

Pgutierrez · June 23, 2017, 03:29:29 PM

Ahh, da crapper!!!
A few suggestions to all:
Every 2-3 years replace the guts (moving parts) of the pump interior cylinder (comes in a nice packet with spring, gaskets, etc). Make sure the spring is in the right place, gaskets lined up exactly where they need to be, DON'T over tighten the screws holding cylinder camp. Otherwise you will say "0h Crap"
Also dump 1/4 vegetable oil into the toilet and DON'T pump out in one cycle. Pump 2X or 3X, have a beer or two, repeat 2-3 more times. Might lubricate the pump cylinder.

Geoffreykwright · July 04, 2017, 08:59:03 AM

This has happened to me. My holding tank vent is on a stanchion on the port side. The vent gets blocked from time to time by spider webs. I've found a small bottle brush works well followed by a splash of Bug-Tek.

KWKloeber · July 05, 2017, 09:12:05 AM

Quote from: Geoffreykwright on July 04, 2017, 08:59:03 AM
This has happened to me. My holding tank vent is on a stanchion on the port side. The vent gets blocked from time to time by spider webs. I've found a small bottle brush works well followed by a splash of Bug-Tek.

Good point on cleaning out speeders and other critters.

All, understand that (black water and potable water tank) vents are a "tube within a tube", that extends up inside the stanchion, to just below the lower life line. The hole at the stanchion base may be open, while the vent tube inside can remain blocked.
In worst case, putting a LITTLE garden hose pressure/flow thru the vent line will back flush the stanchion and clean out the inside tube.

kk

WindyT · August 22, 2017, 04:11:20 PM

Hey folks,

Same deal, hard pumping head. Have guaranteed the black water tank is evacuated both by macerator and pumping it out. I'm afraid it is a blockage problem - either pipes or tank vent. About to roll up the sleeves and confirm... that said, I swear to god that I cannot find the tank vent in the stanchion! I believe it should be directly at base the midship stanchion. Is there a C34 secret handshake I didn't receive upon purchase of vessel? Would appreciate a tip

T

Dave Spencer · August 22, 2017, 06:02:29 PM

Windy,
Here's a pic of my stanchion. Note that I'm holding I upside down in the picture to show the bent plate. It's right above the nav station. You might be able to trace the vent hose by removing the teak facing at the aft outboard cabinet with the sliding doors.

http://c34.org/bbs/index.php/topic,7327.msg49862.html#msg49862

WindyT · August 22, 2017, 07:26:19 PM

Thanks for the pic!
Makes me think my stanchion has been replaced. The starboard midship water tank has a similar vent that was quite easy to find. I suppose I'll go hunting and will let you know what I find.

Regardless, I pumped the tank out and then simply removed the vent hose from the top and still had the same problem = it ain't the vent. Going to cross my fingers its the pumping unit itself and not the tubing between the head and the tank.

Jim Hardesty · August 23, 2017, 04:36:46 AM

QuoteIs there a C34 secret handshake

WindyT ,
There isn't a secret handshake. But. There is the signature you can add to your profile. It helps the posters give better information. Include things like homeport, hull number, year, model, engine, rig, keel etc. Just look what others have added.
Jim

Ron Hill · August 23, 2017, 01:30:10 PM

Windy : Instead of using "Head Lube" I found that spraying some silicone on the large "O" ring on the bottom of the pump handle helps the pump slide up/down inside the pump column - much better.

A thought

Jim Hardesty · October 02, 2021, 09:31:48 AM

QuoteI had a similar problem and it wound up being the valves on top of the handle area, those little brass round things, one side would open and the other would not when put in dry bowl. I bought the entire plunger system, helped for awhile, now when I flush, air and "liquid" sometimes shoots back out of the bowl "ugh", or when I operate the plunger and hold it down, I get a big "sigh" sound.

Exactly the same problem I'm having. With a pump replaced at the start of this season. It goes away if some lube, vegetable oil, is pored into the bowl and pumped to the tank. In the groups experience, will Jabsco help? Who would be a good person to contact?
My original Jabsco worked well.

Jim

Ron Hill · October 03, 2021, 01:18:26 PM

Jim : I complained about the hard pumping a number of years ago. I also complained to Jabsco and accused them of changing the "rubber" composition of the large "O" ring that is at the bottom of the pump shaft. They denied it, but I'm sure of it!!

My best fix is silicone grease (plumbers grease) on that "O" ring.

A few thoughts