We purchased a Lavac after extensive research on the web and discussions on Cruising Bulletin boards. The instructions were rather straight forward but as the years have gone by we've found information that was provided to be lacking. There was never any suggested hose length runs. Lavac suggests 10 pumps with the Guzzler hand pump and then a pause of 3 to 5 seconds for the vacuum to be eliminated; then a couple of pumps to clear the toilet.
They also provide no information on how tight the base bolts are to be. As you can see by the photo the flange that aids in keeping effluents in the toilet is not of the same dimensions all the way around the ceramic base. This caused a small leak into the space where the exhaust hose exits the base and we found a small seeping from the pedestal with accompanying odors. I had at one time tried to torque the bolts that hold the pedestal to the base to the recommended torque value for the bolts but stopped well before reaching the 7 ft lb value. I was beginning to watch the edge of the base distort! I emailed Blakes- Lavac as to how tight to make the bolts and received NO REPLY. That IMHO is reason enough to remove them from an A to a B. Further; we have two Lavac heads on our boat and both bases broke in roughly the same place. I J-B welded the first one together and it's been holding fine. On the other one the cracks were more extensive so I ground out the cracks on both sides of the base and then J-B Welded both sides. I've since ordered two new plastic pedestals.
I've since had the bright idea to have two bases made up in Bronze as then I can tighten enough that there will not be any leaks. In Trinidad where labor is a good value and prices are fair I had an outrageous quote of a $1,000.00 / base (that's in US dollars). I worked hard to not laugh as I exited the shop.
After 4 years: We put the boat on the hard for 6 months. I don't really trust the boat in the water un- attended for long periods of time and we did a great deal of traveling, back to the US, Guatemala, and Peru. When we returned to the boat the absent Gremlin did it's work. One item was the little bleeder valve that Lavac includes for the installation. In their instructions they suggest using the bleeder valve or drilling a very small hole in the hose. I choose using the bleeder valve. Bad choice. Either way you end up with potentially a bad spot in the hose. But since the valve was plugged I asked Lavac what to do and they said" Take a pin and punch it through the hole in the bleeder valve." Easy enough. So I did, and the bleeder valve came out of the hose! Putting it back in a 4 year old hose did not work. Had I simply drilled a hole it would have been an easy fix. I ended up using some of the Atomic Silicone streatch, stick to itself tape and then used the pin to punch a hole into the opening. We'll see how it works.
One other "Gotcha" is the Henderson MK IV pump. Ironically one pump (we have two heads) has lasted the entire 5 years. The other, I've had to rebuild 3 times. The one that has lasted feeds from 7:30 and exhaust at 1:30. The one that I've had to rebuild feeds at 6 o'clock and exhaust at 12:00. I'm thinking that the one with 6 and 12 lets precipitates form and close off / wears out the joker valve. Then with hard particulate incasing the valve the valve eventually fails.
Thus, I've had to rebuild it three times. The instructions are POOR! For example, the two pieces that contain the diaphragm are held together with a plastic nut and two 3" washers. The instructions say to "Finger Tighten" the nut. If you do that the pump will leak and you will not be happy. I tighten mine and still it leaked. I had to open it up and retighten it again. Fortunately I test with all fresh water in the system but it still is a wet mess. The four screws that hold the joker valve in are Sheet metal screws and I never get them tight enough. They have always leaked and then once the unit is fitted I need to trim the hose to tighten the screws adequately.
There seem to be two models of the Henderson MK IV. When we purchased the Lavacs we wanted a drop in backup. So a year later I purchased another Henderson MK IV. The Lavac Hendersons came with the base and the cover connected with Sheet Metal Screws and a drain hole in the no effluent side. The Henderson MK IV I purchased a year later came with nuts and bolts holding the body together and no drain hole in the back side of the diaphram. Lavac Grade B