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Black Water Tank Replacement

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Jonw View Drop Down
Sub Lieutenant
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Joined: 03 April 2022
Location: Gosport
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonw Quote  Post ReplyReply Direct Link To This Post Posted: 04 May 2023 at 13:45
Hi All - a short update on this (for info)

(My 385's problem was the holding tank not draining / draining v v v slowly)

I disconnected the 'exit pipe' which runs from the holding tank to the seacock, from the seacock end.
(I couldn't get access to the jubilee clips on the end at the actual holding tank to undo the other end)

The pipe itself was clear, no scale, no blockages, I rodded it to make sure.

I then wondered if there was scale (calcium carbonate) inside the holding tank.

So I poured in some hydrochloric acid (patio cleaner) and it 'fizzed' incredibly, indicating it was having a strong reaction with something in the tank, probably calcium carbonate. 

I attach a photo.

The level of sea water in the tank is marked by the (low down) blue dots.

The 'fizzing' is marked by the higher up black dots. At times the fizzing reached the metal band and above.

I repeated this process a number of times, until there was no more fizzing when I poured in the hydrochloric acid.

At that point, the tank would drain incredibly fast, and (so far!) reliably!

We've also just had a long weekend on the boat, with multiple people on board utilising the facilities, and all has so far behaved very well, and the tank continues to drain v v fast when set to empty.




Also (for info) when 'rodding' the pipe, it appears that there may be an 'elbow' just inside the holding tank, like a 90 degree turn. (my conclusion based on rodding)

I hope this info may help others in time.

In other news, we had a very lovely few days sailing around the Solent, in light airs, which were just perfect for a shakedown sail / first outing of the season.

Wishing you all happy sailing.

Jon
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Ian2019 View Drop Down
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Joined: 04 November 2019
Location: Montenegro
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ian2019 Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2023 at 04:27
There is a small wire mesh filter in the side hull vent to the holding tank and the filter gets blocked, therefore not allowing air into the tank when draining so a slow drain. I took mine out ages ago and have had no problems.
H385 #317 2014 Tivat Montenegro
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Keakaka View Drop Down
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Joined: 02 August 2020
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keakaka Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2023 at 09:15
I found it is useful to pour 5 litres of water into the deck connection when dumping the tank contents. The extra pressure pushes some of the blockage material out through the seacock. Guests always use too much paper and not enough water. 😥
This is not a rehearsal. Go for it. Kiakaha
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Wild View Drop Down
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Joined: 18 March 2010
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wild Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2023 at 07:57
After to much issues with Wurth blackwater tanks I made a manhole controller hole just on top of the riser tube so I can clean the tank easy and make a SS tool (you can see it in front of te tank) to clean the rising tube from above. The rising tube is the most critical of the tank. There’s always black water in this tube (tank empty our not) And in a warm environment and salty waters this tube get easily blocked with salt- and urinecristals.
The filter in the ventilation cap is stupid. Throw it away.
 



Edited by Wild - 07 May 2023 at 08:03
Wild and Wet
Belgium
545e#268
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Mark&Catherine View Drop Down
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Joined: 18 January 2013
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mark&Catherine Quote  Post ReplyReply Direct Link To This Post Posted: 27 May 2023 at 08:54
I can’t empty my tank now (385), and I can’t see how to change the pipe, I can’t reach the jubilee clips on the hose at the bottom of the tank. Has anyone managed to change the pipe ? 
385 ubulukutu sail number GBR 3350L in Turkey and Greece with Mark and Catherine
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MasterKeil View Drop Down
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Joined: 08 April 2007
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MasterKeil Quote  Post ReplyReply Direct Link To This Post Posted: 27 May 2023 at 17:28
Thats it Ian2019. When my waste tank was depleting slowly, I found this wire cage blocked by bugs and debris. After cleaning the mesh the depleting rate is back to normal.
Hanse 370#640 "Nemesis"
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