Spluttering taps

[Metabarca]

I've renewed all the fresh-water system in my boat, but I'm suffering from spluttering taps: air's getting in.
The set-up is this: two flexible tanks with a valve upstream allowing me to fill either. Downstream of each, there's a shut-off valve so I can draw water from one or the other. The tubes from these then join and go to the pump. From the pump, another Y-connector takes water to the heads and to the sink. I use one tank at a time and when it's empty, close it off. But air is nevertheless getting in. What should I do? Put in non-return valves somewhere along the circuit? Or what? Urgent reply needed: I'm off in two days!

 

[Thistle]

Are you sure it is air getting in? Could it be air trying to get into the tank via the tap? To put it another way: is there a vent in each tank to allow air in to replace water removed?

 

[boatmike]

All those Y connectors are possibly leaving air behind in closed lines. Open all connectors so that you are pulling from both tanks, then run both taps till the spluttering stops. Then, still with both taps running, close one tank isolator valve for a minute or so then open it and close the other. That should purge the system.
If you have trouble after that you need to find the air leak.

 

[Andrew_Fanner]

Do you use an accumuator tank in the system?

 

[Metabarca]

To answer all: air via the tap: no, because I see the bubbles travelling towards the taps. There are no vents in the tanks, but the tanks themselves are flexible so they simply collapse.
There's no accumulator tank.
I'll try purging the system as boatmike says, but I'm pretty sure there must be a leak in the system (in the isolator valves). Nevertheless, with the pump off, the water will run down the tubes back to the tanks through the force of gravity. That' why I was wandering whether non-return valves near the tanks would help, by holding the water in the tubing between tank and tap. Ideas?

 

[Rivers & creeks]

[ QUOTE ]
To put it another way: is there a vent in each tank to allow air in to replace water removed?

[/ QUOTE ] They are flexible tanks, so not a problem.

We get this after filling our flexible tanks; either leave the tanks for an hour or run some more water through. One way to test is to completely run through your tanks, if it is still spluttering after 3/4 of the tanks are run through then there is no more air to purge in the new system! And then you do have a leak. The first place to check are the connections from the tanks to the pump; the reason is that the pump is 'sucking' from these pipes and air is most likely to enter at these points; down the line then the pump is 'pushing' and so air cannot enter until the pump is off. What this means practically is that even if you run through both your tanks of water and the taps are still spluttering, the leak must be between the tanks and the pump.

Good luck.

 

[Rivers & creeks]

[ QUOTE ]
with the pump off, the water will run down the tubes back to the tanks through the force of gravity

[/ QUOTE ] ??? That should NOT happen! The pump should operate as a non-return valve. Are you sure that the water is going back to the tank or out through the leak? Just a minor point but you say you can see bubbles, all the pipes should be opaque, even small amounts of light to water sitting in pipes will allow growth of bugs and slime; perhaps put water purifying additives in more often.

 

[Danny]

Sounds to me as though it could be a stuck valve in the pump allowing water to flow back to the tank(s). Also, do you have a filter before the pump? These can leak and let in air causing spluttering.

 

[Metabarca]

The pump is new; I'll have to check if the water is actually flowing back past the pump, or whether is bubbling up through it towards the taps. No filter before the pump.
I suspect the isolator valves...

 

[Bilgediver]

Are you sure that the flexible tank outlets to the pump are completely covered with water.

I saw a similar installation where the tank outlet was too near the surface of the water due to the way the tank was sited and the position of the outlet.


John

 

[charles_reed]

Flexible tanks

don't work like that - they collapse as they empty.

It's a good idea to have the outlet at the lowest point of the installation - that (or a leak downstream of the pump) I suspect may be the problem.

 

[ccscott49]

Re: Flexible tanks

Charles, off topic but do you know if flexible fuel tanks are still available, as in for atlantic crossing, then roll up?

 

[rogerthebodger]

Re: Flexible tanks

this is what i think you are looking for

 

[ccscott49]

Re: Flexible tanks

That is exactly what I'm looking for! Thank you! Vetus do them as well, but these ones look really well made!

 

[tross]

Re: Flexible tanks

I have exactly the same problem and it is due to the outlet pipe ( top mounted) not picking up properly - try putting a weight around the outlet pipe to force it into the water

 

[rogerthebodger]

Re: Flexible tanks

I came across this company local to me and wondered if they could do some flotation bladders to keep my new yacht from sinking if holed, but I also wonder if the materal would be proof against diesel fuel for the reason you are thinking about.

 

[Metabarca]

Yes, they're certainly at the lowest point.
The problem must be in the valves, so I'll put a little silicon in as a gasket to try and seal them better. Thanks all!

 

[charles_reed]

Re: Flexible tanks

Try Plastimo France - 0033 2978 73636.

They'll know if they've any in stock. then get them to send them to your favourite chandler

 

[pampas]

When you nevt fill the taks open all valves and fill till the water overflows fron yap this will ensure all or any air is out of the system. Shut the tap suply off first then the fill vlv, and see when in use if this has cured the problem.