Water volume difference between Groco HF, Raritan SF PHII Jamsco Twist n Lock

Apr 5, 2009
3,102
Catalina '88 C30 tr/bs Oak Harbor, WA
My boat only has an 18-gallon black water tank which fills far too quickly and we are constantly struggling with finding a pumpout.
The current head is a Groco HF which was purchased in 2005 and does not pump well.

Assuming that all heads are pumping as they should, which one will use the least amount of pump water to clear the bowl?
I am in favor of the PHII but my wife is more of "stick with what you know, HF". Or the TnL for half the price.

Which of the three is most likely to use the least water to clear the bowl Assuming that everyone on board is concerned about not filling the tank quickly.
 
Dec 2, 1997
8,918
- - LIttle Rock
The user controls the amount of flush water used by any manual toilet. Always using the wet mode except to move the last bit of water out of the bowl uses the most water. Learning how to flush using the dry mode reduces the amount of flush water going into the tank, increasing the number of flushes the tank can hold by 50% or more.

I've posted instructions for doing that several times in the 25 years I've been here. We both can spend a lot of time searching for 'em or I can spend a lot of time retyping 'em, but everything you need to know about flushing and maintaining a manual toilet is in the "Flush With Success" section of my book... (See link in my signature below...or, if you want the ebook version, you can get it from Amazon). Be sure to read "joker valves 101." in the Maintaining chapter.

As for which toilet to replace the Groco...the Raritan PHII (current version has been renamed "PH SuperFlush" It still uses tried and true PHII pump, just has a new base with a mounting bolt pattern that matches most other manual toilets. ) has remained the top rated manual toilet since they introduced it in 1983. It's not only the most powerful--can move twice the volume with half the pump strokes--but will easily provide 20+ years of reliable trouble-free service if it's just kept well lubricated, gets a new joker valve annually, and a rebuild kit (approx $60) every 5-6 years. You're lucky to get 3 trouble free years out of a TnL--which, btw are all made in Mexico now with materials and components sourced from China. Raritan still makes everything in the New Jersey plant.

Fisheries in Seattle has it for $450...you can pick it up from them so shouldn't have to pay any shipping, which would add a lot 'cuz toilet bowls are HEAVY!

You're welcome to give me a shout via PM if you have more questions.

--Peggie
 
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Apr 5, 2009
3,102
Catalina '88 C30 tr/bs Oak Harbor, WA
Thanks Peggy.
Fisheries actually delivers free to my marina so that makes it even better. It sounds like we would need to do some serious "relearning" on how to flush with the PHII if it pumps twice the volume with half the strokes. That would be a 4x increase if we continue to pump like we have for the past 24-years! :facepalm:

On an average, how many pumps do you recommend for liquids and solids with the PHII. Our discharge hose is only 3' long with a slight upward slope.
 
Dec 2, 1997
8,918
- - LIttle Rock
That makes a lot less of a difference if water is added to the bowl ahead of the "deposit.' If your toilet isn't designed to bring in water and hold it, use a beer cup from the sink. If the water runs out as fast as you add it, it's way PAST time to replace your joker valve. Its condition also has a major impact on the efficiency of manual toilets.

Merry Christmas!
--Peggie