Tuesday, July 19, 2011

Forward heads revisited......

A loonnggg time ago I had planned to give the forward heads its own holding tank. After much cutting and grinding I realized that this was going to be more trouble that it was worth. While I accept that holding tanks are a necessity I consider them a major PITA. Having two would just double the experience. In any event I need the space for the bow thruster.

As per LAVAC drawings I had not installed an antiphon valve in the waste hose, this was a mistake. The water siphoned back into the bowl and while it did not overflow it did back-flow waste from the hose with the inevitable smell.

Antiphon valve now installed. All hoses/pump etc. surface installed for ease of maintenance. Wife not majorly impressed but she won't be maintaining it AND its the boy heads.

In keeping with the "boy heads" element it will pump directly overboard (where legal) or back to the holding tank in the engine room. As I hate "Y" valves I have copied this system from another W42.


Nahanni said...

Is it a vented loop type anti siphon valve or is it a one way valve ?

I don't see how the anti-siphon valve would solve this problem.

If waste water can move backwards through your pump it will do the same when the vent on the anti siphon valve opens.

If it's a one way valve, you are just adding another valve to the two that are already in the pump.


The Incredible Hull said...

Hi John

No, its a vented loop (anti-siphon valve).

This is an excerpt from a Don Casey Article:

Vented Loop; If your head is mounted below the waterline, or if it moves below when the boat heels, you must have a vented loop in a discharge line that connects to a through-hull fitting. Otherwise, if the head's internal valves are held open by debris-an inevitable occurrence-water will siphon back into the boat. Poor head installations sink boats every year. Mount the vented loop so it will remain above the waterline at all heel angles. Clean the anti-siphon valve regularly to keep it functioning.

Nahanni said...

I agree that the vented loop is a good safety measure in case of pump failure, but if waste can move backward through your pump then it is failing.

The Incredible Hull said...

Agreed, evev though it's a new pump I will check the joker valves ASAP. This is why it's installed on the bulkhead.