Holding tank question (Peggy are you there?)

[jfm]

Our holding tank fills up in a couple of hours with no use. There is no sign of flush water leaking and filling it. However, the seacock in the discharge-to-sea pipe is normally left open. I am guessing therefore the non return valve (assuming there is one?) in the discharge pipe must be stuck open a bit.

Does this sound correct diagnosis? (I'm not on the boat currently, so doing this diagnosis by remote control) Any other ideas?. How are these non return valves constructed - is it a flap type valve and could some crud have got caught in it so preventing it closing/seating properly? Are they cheap plastic devices, so I should just buy one and take it down to swap it? The components are generally Sealand, and the discharge pipe is I guess 1.25 inch diameter approx, with a macerator pump, the usual set up. How many pairs of rubber gloves and gas masks will I need to do this job?

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[jhr]

Surely all you need to do is ring up Fairline, who will immediately and cheerily identify the fault, air courier the appropriate spare parts to the SoF and arrange for them to be fitted to your craft with a smile?

Or have I misunderstood what happened last time? /forums/images/icons/smile.gif

<hr width=100% size=1>Je suis Marxiste - tendance Groucho

 

[Bejasus]

your system although not the same model should work either like <A target="_blank" HREF=http://www.jabscoshop.co.uk/images/about/toilet_option4.gif>this,</A> or a combination of similar plumbing methods. If you have no water running through your toilet then it seems like a syphoning problem from outside. Perhaps your vent in the anti-syphoning loop is clogged. Not aware of non-return valves in the plumping, except for joker type valve in the toilet, although I am familiar with Jabsco rather than Sealand. Hope this helps.


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[powerskipper]

We are advised to tell all people that they are better to close there sea cock to the holing tank except when emptying it due to the fact they can back fill. Think this is what is happening.

<hr width=100% size=1><A target="_blank" HREF=http://powerskipper.mysite.freeserve.com/>http://powerskipper.mysite.freeserve.com/</A>
Julie

 

[jfm]

jhr hits raw nerve

jhr if you were within half a mile I'd come round and thump you for that response

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[Deleted User YDKXO]

I agree with h00. The discharge pipe should have a swan neck in it to stop back flow. I've never seen a non-return valve in the system. As you say, I would have thought its asking for trouble
Easy to find out whats happening. Just close the seacock and see what happens

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[jfm]

Thanks Deleted User and h00. I see, there is no non-return valve, just a big loop. Or at least there should be. Makes sense. I'll check we have that loop of pipe. If we do, I'm confused as to how it is filling up with sea.......

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[Bejasus]

there should be a little anti-syphon valve in the top of the loop, which allows air in to break the syphon.

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[Deleted User YDKXO]

I take it you have freshwater flush toilets. Therefore, I think you should open up the holding tank and taste the contents. Maybe this is a job for the crew. I'm sure this will confirm whether you have a seawater or freshwater leak

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[jfm]

Thanks for that Deleted User. With such a knack for helpful advice, you could get a job in Fairline customer support.

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[jfm]

In which case it sounds like the antisyphon valve is stcuk closed or blocked, thus allowing seawater to syphon back into tank. I'll check it. Thanks Only problem is, I bet it's in an inconvenient place........

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[Jim44]

I know this is not relevant and probably covered before but i am confused do you have a Fairline or a Sunseeker?

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[HeadMistress]

Your problem is indeed the open thru-hull. It should be kept closed at all times except while dumping the tank.

There's no non-return valve in that line, nor should there be (and don't even THINK of installing one in an attempt to avoid the inconvenience of having to open and close the thru-hull!) However, there should be a vented loop (anti-siphon device) in that line between the pump and the thru-hull that's at least 8-12" above the waterline. However, while a vented loop will prevent water from rising in the line and flooding the tank while the boat is at rest, it will not prevent water from being forced up the line into the tank by the pressure of the hull against water while underway--an effect known a "ram water"--and neither will ANY pump...the best any pump can do is slow it down a bit.

Head and tank thru-hulls left open while no one is aboard is the #1 cause of boats sinking in their slips. So keep that thru-hull closed at all times, opening it only to dump the tank, and then close it again immediately. A bit more inconvenient than just pushing a button when the "full" light comes on, but beats the socks off arriving at the dock to find your boat sitting on the bottom...or even a toilet bowl overflowing waste in the head.

<hr width=100% size=1>Peggie Hall
Specializing in marine sanitation since 1987

 

[jhr]

Re: jhr hits raw nerve

Oops. Sorry /forums/images/icons/smile.gif. Being sarky, partly due to my stunned disbelief at your previous post and the lack of concern for the customer that it represented. There was (and maybe still is) a famous architect called Owen Luder, who memorably described one of his hideously ugly buildings as saying "sod you" to the general public, and we seem to have the marine industry equivalent here.

Glad to see that Peggy Hall has come up with the goods for you.

Re coming round and thumping. I am in Central London at the moment hence, possibly, quite near you? But I am leaving to go home. Now.

<hr width=100% size=1>Je suis Marxiste - tendance Groucho

 

[jfm]

Thanks peggy. I have not yet inspected it first hand but my partner is on the boat today and gave me the following information.

1. The pump is a macerator pump Johnson TA3P10-19. You probly know it, but if you enter that in google you get all the info. This pump has no internal non-ret valves or duckbills like say the Sealand T series.

2. There is no non return valve in the discharge pipe and

3. There is no loop-up above the waterline, nor is there any siphon-breaker vent in the pipe.

So i conclude the installer's intention is that the seacock is always shut except when dumping. Nice of them to tell us.

But when i spoke to the UK supplier/importer of the Johnson pumps about an hour ago, he said he can supply a plastic non return valve for the discharge pipe, so I dont need to shut the seacock. I bought one over the phone, they're gonna mail it to me. It fits by cutting the pipe and using jubilee clips

You dont recommend a non return valve. But why? If I leave the seacock open and the non return valve fails, sea water will fill the system but the rims of my toilet bowls are above waterline so boat will not sink. So why worry?

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[stellican]

The dicharge seacock must be kept closed and only opened when dicharging the tank the system will most likely have a flap type valve in the outlet line which tend not to close properly. Instances have been known of the tanks back filling and leaking into the bilges via the tank inspection hatch. On some of the American built boats the handle to the seacock are tie wrapped closed, they even supply a quantity of spare tie wraps for future use after opening the seacock!

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[jfm]

Fairline Squad 58. It looks a bit sunseekery in the little picture, sorry. I think profile is up to date but will check.

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[jfm]

think I\'ll have to give in and close the seacock

I hate opening and shutting seacocks. My arms cant reach them when reaching down thru the floor hatches. (I mean cos the bilges are deep, not cos my arms are short). But I can see I'm gonna have to adop the practice of opening/closing this seacock, dang.

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[HeadMistress]

Keeping ALL seacocks closed except when in use--and especially when away from the boat--is just basic good seamanship and boat maintenance. Stellican's reply is spot on...there is NO "right" way around keeping the seacock closed except when in use.

A non-return valve in a toilet or tank discharge line is just asking for problems because waste is sticky and also because, while macerators and diaphragm pumps "puree" waste they don't completely liquify it...so bits of waste and TP can get stuck in them and even clog the line. But you've already bought one, and it's unlikely that we'll talk you out of installing it...'cuz you don't want to do what should be done, only find a way around it.

Good luck...

<hr width=100% size=1>Peggie Hall
Specializing in marine sanitation since 1987

 

[EME]

Come on Peggy !!

What do you expect? JFM is a severely heavily qualified engineer who is non practising as he bright enough to make his money elsewhere ! Bit like people with loads of boating quals and no experience really -

He's going to kill me for this one.

<hr width=100% size=1><font color=blue>I am WHAT I say I am</font color=blue>