Shoreside pump out of holding tank

[skyflyer]

I'm re-commissioning our holding tank which was decommissioned some years ago when the macerator pump seized, not least because we will be going cross channel this season and I gather they are a bit more fussy about that sort of thing!

The fairly standard diverter valve arrangement permits the toilet waste to go overboard or to the tank.

When it comes to emptying the tank there is a macerator pump to pump it overboard and a deck fitting to allow a shore pump out.

I have never seen or used a shore pump out so dont know whether it is a long tube that dips into the tank or some form of suction device that sucks the waste up the pipe to the deck fitting?

The reason that I ask is that the arrangement as it stands is that the "emptying" pipe from the tank goes to a T junction. The "through" part of that junction is to the macerator - ie the cross of the tee. The flow has to turn through a right angle to get to the pump out pipe.

A (bad) picture still paints several hundred words!

I am thus concerned that if a long tube needs to be inserted to pump out it wont get much past the T junction and this is located quite near the top of the tank level anyway.

Alternatively if it is a giant sort of vaccuum cleaner, is there not a risk that the small vent pipe (not shown in drawing, but about 1/2" internal diameter to top of tank) will collapse and the tank will implode under the suction?

Hopefully someone here will have used these shore pumps before and can explain?

 

[eagleswing]

shore pumpout

as i understand your diagram there is a T fitting and the upper of the T is the old macerator (likely installed when folks used the macerator to pump waste from the holding tank directly into the sea ) . when the macerator was used , there would be an air seal at the 'waste' deck fitting and the macerator vacuums the contents from the holding tank and pushes it thru the seacock.

presumably, there is a seacock that would be open if you were using the macerator to pump out your tank. since the waste deck fitting alllows an air seal, the macerator can then pump out the tank thru the seacock.

Q"....I am thus concerned that if a long tube needs to be inserted to pump out it won't get much past the T junction and this is located quite near the top of the tank level anyway..."
A -- this waste deck fitting is where the huge vacuum tube would be inserted for a shore pump out... the fitting for the shore vacuum is a plug type fitting with a tightening mechanism to form a good seal to your waste port. . the shore fitting is about 4 inches long. this fitting doesn't extend all the way into the tank through the pipe. shore pumpouts work on vacuum , as the pumpout pipe of your tank is below the surface of the liquid slurry being pumped and the pipe runs to your deck fitting ..the shore plug inserts into your waste fitting and hopelully forms an airtight seal. without a good air seal, the vacuum generated by the shore pump can't remove the contents of your tank up thru the deck fitting. (i carry some extra plastic bags and duck tape to wrap around the seal of the shorepower plug , which plug tends to get worn and not form a good seal, resulting in the 15 year old dock attendant telling you your boat is at fault when his pumpout pump doesnt work . but it failed to pump your tank BECAUSE their old deckplug did not get a good seal...

the vent in the holding tank is quite adequate to allow enough air to get in to prevent tank collapse. as the tank contents are being displaced out thru the shore vacuum pump out, air comes in to the tank. (assuming you don't have a wasp nest or bird nest in the vent line for the tank ?)

but i would worry that if you have an old macerator that hasn't worked in a while, the pump body may be cracked. this could lead to a possible air leak and loss of suctioning power : when the shore pump tries to empty your holding tank, it is trying to suck both liquid out of the tank, and is sucking air coming in from the broken macerator.... solution: take out the old macerator completely and connnect a solid piece of sanitation hose in where the mac used to be. (forgetting to winterize a macerator may cause this situation when you most need an operable pumpout...)

note that there is often an external screwdriver slot in a macerator. you can turn the slotted head screw to move the cutter blades to free them and perhaps save your pump.

 

[skyflyer]

Thanks. I have a new macerator pump to fit already as many (most?) uk marinas do not seem to have pump out facilities we still need to macerate and discharge when out to sea. I am guessing you are from USA where pump out is common. When I did some sailing in Florida we were told no discharge within 8 miles of the shore! However I think this will come to Uk eventually - one of the reasons we are re commissioning our tank!

 

[Tranona]

Couple of observations. First your vent is far too small - should be minimum of 25mm. The pump out is vacuum - usually the pump out is a separate dip tube that goes from the top of the tank to near the bottom. Second, you will not find many places anywhere that have pump out facilities, despite all the hype, so you will more often be discharging at sea, so reliable pumping is more important. Most people minimise the use of the holding tank by using shoreside facilities as much as possible.

 

[skyflyer]

The vent pipe is manufacturers fit. However probably 19mm not 12mm as originally posted

Yes of course we use shore facilities when able but when moored on a buoy or isolated pontoon halfway up the Carrick Roads or on visitors moorings at Fowey and caught short, it is rather inconsiderate to discharge overboard!

 

[Tranona]

Yes, 19mm is common, but recommendation is now min 25mm, partly to vent while using pump out. Not suggesting you discharge into anchorages, but your original post said you were re-commissioning system because you were going abroad. Just pointing out that (like the UK coastal areas) there are very few pump out facilities, even in areas where discharge is in theory banned.

 

[skyflyer]

looks like we will need to making regular trips out to sea then

 

[eagleswing]

alternatives...

illegal waste discharge here in the US is punishable by large $$$ fines.. our 30 year old boat had had no holding tank installed by the manufacturer. we fitted a very small Todd 6 gallon gallon holding tank with a Y vave system allowing it to be directly pump out by shore vacuum , or pumped into a portable discharge container. . since the holding tank is translucent and easily accessible, we were able to tell the level of contents by shining a light behind the tank. if no pumpout was available , we had installed our macerator with a Y valve allowing us to use the macerator to pump the holding tank contents into a (dedicated )portable gasoline-style container. (this container was then used to dump holding tank contents into the nearest (legal) toilet or RV discharge station . using liberal amounts of Sealand head deodorant , and flushing the head with freshwater from a dedicated tank instead of seawater, resulted in very minimal odor in the holding tank itself. the macerator was so powerful that it could empty the tank in less than a minute into our portable container. though carrying our holding tnak gas container on shore was not pleasant, it certainly beats large fines or an unusable head when the holding tank is too full.

 

[Tranona]

looks like we will need to making regular trips out to sea then

Good excuse! The only area where they have got holding tanks and pumpouts really sussed is BWB canals. But narrow boats have the space to fit decent tanks rather than the odd shaped little things we end up with on yachts.

 

[skyflyer]

eagleswing - the powerful macerator emptying into a 5 gallon portable jerry-can seems like a disaster waiting to happen it you're not holding the hose carefully and ready to switch off the pump instantly!