Pumping the Bowl Dry

[theArchitect]

I have a new used boat. When I pump the head dry, pressure builds in the lines enough to push the rubber diaphram out on the pump out handle. I pumped the tank out to confirm that it wasn't full but, I get the same symtom. Pumping out went well so I assume the vent line isn't clogged. Any ideas? Thanks!

[Cruisingdad]

You can start by rebuilding the pump. Depending on the model, this is not that tough. However, in some cases, it is cheaper just to replace the whole thing, bowl and all.

If you can pump wet, I cannot see why you cannot pump dry. Sounds like a valve sticking. I will warn you, on some heads, the lever to switch to dry bowl is tricky and has to be all the way up (or back). We have a Wilcox and it is like this. It can look like it is up, but it is juuuussssst out of dry bowl. The effect is when you push down on the handle, it hardly moves like there is a whole lot of pressure behind it. It that is your symptom, perhaps it is as easy as the lever is not quite in the right position. Try jiggling it as you push down to see if that helps. If not, rebuild or replace is my guess.

Hope that helps. Nothing wears on a skipper like a crappy crapper. (smile)

- CD

[theArchitect]

I can pump it wet and dry but it seems to put a lot of pressure on the lines at the pump handle used to pump the holding tank contents overboard (the pump handle at the head operates correctly). The hoses hiss and the diapharm balloons out. Opening the seacock that is used to pump directly overboard releases the pressure.

[TrueBlue]

Check the anti-siphon valve at the very top of the effluent hose, as it loops up above the waterline. It's possible this is either clogged, or needs to be opened a bit more to displace more of the air pressurized in the system during pumping.

[CoralReefer]

You may have your Y valve opened to overboard if the pressure is released when you open the seacock. Try moving your Y Valve to another position to send waste into your holding tank.

[Cruisingdad]

Hmm, after reading that, I would wonder whehter you might have a clogged vent line or TB might be right. When you pumped out, did it suck the bowl dry?

Try TB's suggestion first. It will likely be the easiest. If not, I would guess a small clog in the sewage line to the holding tank or a clogged vent.
If it is an old system, it is not all that un-normal for Ca deposits to restrict flow and cause clogs.

- CD

[theArchitect]

Thanks for all of the feedback! When I pumped out, the bowl was sucked dry.
I have tried turn the y-valve to both positions and it didn't make a difference on the pressure building in the system.
I tried turning the anti-syphon valve last night in hope of removing it and checking for a clog but it just rotated and never got any closer to coming off. Shouldn't it unscrew? I'll try again tomorrow night.

[theArchitect]

The vent fitting is clogged. I can just barely reach it from inside the boat. Any ideas on how to unclog?

[LaPlaya]

If u can remove the line compressed air may do it. If not possibly hi pressure water? Good luck AL

[Sapperwhite]

If you can remove it, replace it. It will only cost a couple of bucks, and a few hours, but save alot of heartache (and poopy smells).
I also have a new old boat. When I first tried the head there was a problem, no water would pump in. I could fill the bowl with a bucket and pump it out, but nothing would come in. I decided to rebuild the pump. As soon as i got the pump apart I found a huge wad of seaweed plugging the inlet side of the pump. It took me about three seconds to decide to install a strainer in the suction line to pre-empt doing that nasty job again in the near future. Messing with heads is nasty. When the part wears out replace with new if it's cost effective. It beats messing with the same thing again in two months.