Integrated water tank internal outlet pipe replacement

[MardyBum]

We're currently de-rusting our integrated water tank and are planning to paint with 2-pack epoxy (as we have done for the bilge bays) and then use a separate smaller tank for drinking water. The boat is out of the water in a couple of weeks and we've a welder booked in to fill a number of deep-ish pits.

 

The outlet pipe (top left in pic below) inside the water tank is all bunged up with rust and pretty gross. I was thinking of cutting it off and asking the welder to weld on a new one, perhaps pre-painted with epoxy as much as possible (up to the point of the weld area, obviously).

 

Is there a better way of doing this? I'm not really sure what best practice is here, and I've effectively got the opportunity to start again with it! Can I/Should I use some sort of plastic piped or ask him to weld on maybe a threaded hose tail connection through the tank wall with a hose down to the tank floor?

 

Thanks folks.

 

 

[Tony Brooks]

No idea about "better" because most tanks seem to have welded in pipes of one sort or another, but it occurs to me that you could drill a hole close, but not quite at the bottom of the bulkhead and fit a metal (brass/bronze) skin fitting with soft sealing washers, perhaps with adhesive sealer, either side. That way you would not need a welder now or in the future, but it would be slightly more likely to leak. This is just an idea, not a recommendation. The hole will have to be high enough for the fitting's flange, washers and nuts to clear any weld line along the bottom of the bulkhead.

[David Mack]

1 hour ago, MardyBum said:

or ask him to weld on maybe a threaded hose tail connection through the tank wall with a hose down to the tank floor?

I would fit the outlet close to the bottom of the tank, so that the water flows under gravity, rather than having a dip pipe (hose) in the tank.

An internally threaded socket could be welded to the outside of the tank, and you could paint the threads with the same epoxy as used for the tank. Then screw on a brass fitting from the outside to connect to the water supply pipework. That way there should be a minimum of exposed steel in the connection and less chance of it getting gunked up with rust.

[PaulJ]

54 minutes ago, David Mack said:

I would fit the outlet close to the bottom of the tank, so that the water flows under gravity, rather than having a dip pipe (hose) in the tank.

An internally threaded socket could be welded to the outside of the tank, and you could paint the threads with the same epoxy as used for the tank. Then screw on a brass fitting from the outside to connect to the water supply pipework. That way there should be a minimum of exposed steel in the connection and less chance of it getting gunked up with rust.

Speaking as someone who likes to stick bits on properly with weld and I have always done it exactly how David Mack describes.

Having read a few threads on this though I think I would now be tempted to weld on a stainless fitting (think Magnetman suggested this) and save anymore future maintenance of cleaning the threads, reblacking them along with the tank etc.

 

[Bee]

Personally I would do pretty much as Tony suggests, Buy a brass 'Tank connecter' from Screwfix, clean up the surfaces so they are clean and flat, fix a bit of in 15mm copper with a hose tail on it, fix and forget, I wouldn't worry about trying to get a tube right down to the tank bottom, the last couple of inches are neither here nor there as far as capacity is concerned. As for capping off the disused pipe it depends on what is on the end of it, if it is threaded then a trip to a plumbers merchant should provide you with a cap of some sort.

[Tracy D'arth]

I would drill a hole and use one of these:-  https://www.screwfix.com/p/hep2o-plastic-push-fit-tank-connector-15mm/4635f

 

No more rusting or problems with dissimilar metal corrosion.

[ditchcrawler]

1 hour ago, Tony Brooks said:

No idea about "better" because most tanks seem to have welded in pipes of one sort or another, but it occurs to me that you could drill a hole close, but not quite at the bottom of the bulkhead and fit a metal (brass/bronze) skin fitting with soft sealing washers, perhaps with adhesive sealer, either side. That way you would not need a welder now or in the future, but it would be slightly more likely to leak. This is just an idea, not a recommendation. The hole will have to be high enough for the fitting's flange, washers and nuts to clear any weld line along the bottom of the bulkhead.

Or even a proper tank flange like an Essex Flange.

2 hours ago, MardyBum said:

We're currently de-rusting our integrated water tank and are planning to paint with 2-pack epoxy (as we have done for the bilge bays) and then use a separate smaller tank for drinking water. The boat is out of the water in a couple of weeks and we've a welder booked in to fill a number of deep-ish pits.

 

The outlet pipe (top left in pic below) inside the water tank is all bunged up with rust and pretty gross. I was thinking of cutting it off and asking the welder to weld on a new one, perhaps pre-painted with epoxy as much as possible (up to the point of the weld area, obviously).

 

Is there a better way of doing this? I'm not really sure what best practice is here, and I've effectively got the opportunity to start again with it! Can I/Should I use some sort of plastic piped or ask him to weld on maybe a threaded hose tail connection through the tank wall with a hose down to the tank floor?

 

Thanks folks.

 

 

If you are going to all this trouble to do a good job why not use a potable water 2 pk paint so the water tank can be used for anything

[Ex Brummie]

My boat has a 1/2" BSP socket welded into the top of the tank, into which is screwed a 1/2" BSP x 15mm connector with stop in the connector opened out so that a piece of 15mm Hep2o can be fed through as a dip pipe that picks up from the mid/front tank which means you have a catch area where any sediment settles. This also has the advantage of a water pump mounted level with the top of the tank, so in the event of a possible fault with internal pipework does not result in a tankful of water syphonong into the boat.

[MardyBum]

6 hours ago, Tony Brooks said:

No idea about "better" because most tanks seem to have welded in pipes of one sort or another, but it occurs to me that you could drill a hole close, but not quite at the bottom of the bulkhead and fit a metal (brass/bronze) skin fitting with soft sealing washers, perhaps with adhesive sealer, either side. That way you would not need a welder now or in the future, but it would be slightly more likely to leak. This is just an idea, not a recommendation. The hole will have to be high enough for the fitting's flange, washers and nuts to clear any weld line along the bottom of the bulkhead.

I think this or what @Tracy D'arth suggested is what I'm leaning towards at the moment, although interesting idea about fitting at the top of the tank with a dip hose, from a failure protection perspective I quite like that too - thanks all!

 

@ditchcrawler if I could find a surface tolerant potable epoxy that's exactly what I'd be doing, but I've so far come up short. All the previously recommended products have been removed from sale in recent years. If you know of one still available, please do share 🙂

[Tracy D'arth]

I know several people who have used epoxy 2 pack blacking inside water tanks without any problem with potability or taint of the water.

I also know several who use epoxy glue to fix their dentures and they are still around years later. The stuff you can buy for replacing dental caps and fillings is epoxy.

They stick cuts in hospitals with superglue ( I know that is isocyanate, not epoxy ) so perhaps all these chemicals are not a health problem.

[ditchcrawler]

1 hour ago, Tracy D'arth said:

I know several people who have used epoxy 2 pack blacking inside water tanks without any problem with potability or taint of the water.

I also know several who use epoxy glue to fix their dentures and they are still around years later. The stuff you can buy for replacing dental caps and fillings is epoxy.

They stick cuts in hospitals with superglue ( I know that is isocyanate, not epoxy ) so perhaps all these chemicals are not a health problem.

The problem is the market is not big (lucrative) enough to make it worth while spending the money getting it testing and approved. 

[blackrose]

9 hours ago, MardyBum said:

We're currently de-rusting our integrated water tank and are planning to paint with 2-pack epoxy (as we have done for the bilge bays) and then use a separate smaller tank for drinking water. 

 

Which epoxy are you going to use? If you use a water potable epoxy you won't need to have a separate tank for drinking water. If you don't use a water potable epoxy the water will be tainted and you won't even want to use it for cooking or washing. 

[ditchcrawler]

Search | Rawlins Paints

[blackrose]

2 hours ago, MardyBum said:

@Tracy D'arth

 

@ditchcrawler if I could find a surface tolerant potable epoxy that's exactly what I'd be doing, but I've so far come up short. All the previously recommended products have been removed from sale in recent years. If you know of one still available, please do share 🙂

 

Have you looked at Jotamastic tankguard DW ? The only downside is it's only available in 15 litre units, but perhaps you could split it with someone else who's doing the same job?

 

https://www.smlmarinepaints.co.uk/products/tankguard_DW?gad_source=1&gclid=Cj0KCQjw2uiwBhCXARIsACMvIU27KqaXNaGWAfDB-6xW9wYNSf7-d7B-lSBrjnDzknBtDiX6oOKVc2UaAn0aEALw_wcB

 

2 hours ago, Tracy D'arth said:

I know several people who have used epoxy 2 pack blacking inside water tanks without any problem with potability or taint of the water.

 

Which epoxy did they use? 

 

They may claim there's no problem but who knows what they may be ingesting.

 

I wonder why didn't they just use the correct product for the job? What's the advantage of using the wrong product?

 

 

28 minutes ago, ditchcrawler said:

The problem is the market is not big (lucrative) enough to make it worth while spending the money getting it testing and approved. 

 

With bitumen backing that's correct because there's no difference between the stuff you slap on the hull and the stuff tested and marketed as suitable for water tanks.

 

However when it comes to epoxies there's a clear difference between the chemical solvents used in "regular" epoxy paints and "solvent-free" water potable epoxy.

Edited April 13 by blackrose

[MardyBum]

54 minutes ago, blackrose said:

 

Have you looked at Jotamastic tankguard DW ? The only downside is it's only available in 15 litre units, but perhaps you could split it with someone else who's doing the same job?

 

https://www.smlmarinepaints.co.uk/products/tankguard_DW?gad_source=1&gclid=Cj0KCQjw2uiwBhCXARIsACMvIU27KqaXNaGWAfDB-6xW9wYNSf7-d7B-lSBrjnDzknBtDiX6oOKVc2UaAn0aEALw_wcB

 

 

Yep - SML were my first call, but they said I would not be able to get the surface prep good enough without grit blasting - apparently it's not surface tolerant (ike Jotun 90 is for example).

Edited April 13 by MardyBum

[ditchcrawler]

30 minutes ago, MardyBum said:

Yep - SML were my first call, but they said I would not be able to get the surface prep good enough without grit blasting - apparently it's not surface tolerant (ike Jotun 90 is for example).

The link I posted is surface tolerant 

 

[David Mack]

12 minutes ago, ditchcrawler said:

The link I posted is surface tolerant 

 

The general description says that, but in the detail it says "For immersion service: steel; blast cleaned to ISO-Sa2½".

In practice you may well get away with a lesser standard of preparation, but no manufacturer or supplier is going to say that as they don't want any responsibility if the paint system fails.

[MardyBum]

12 hours ago, ditchcrawler said:

The link I posted is surface tolerant 

 

 

Thank you!! 

 

I will give them a call on Monday 👍🏻

 

I had looked at Rawlins before, but evidently not thoroughly enough!

 

Regarding the new outlet fitting, I'm gonna get the old one welded up and then fit a new one at the top of the tank with a dip pipe. I figured that will make for easier serviceability and reduce the risk of a full tank of water leaking into the bilge should there be any kind of fitting failure (thanks @Ex Brummie).

 

Will post some follow up pics in due course.

[Tracy D'arth]

4 hours ago, MardyBum said:

 

 

 

Regarding the new outlet fitting, I'm gonna get the old one welded up and then fit a new one at the top of the tank with a dip pipe. I figured that will make for easier serviceability and reduce the risk of a full tank of water leaking into the bilge should there be any kind of fitting failure (thanks @Ex Brummie).

 

 

It will still syphon the tank contents into the boat!

[Alan de Enfield]

5 minutes ago, Tracy D'arth said:

It will still syphon the tank contents into the boat!

 

Absolutely - unless the pump is above the tank water level.

(My pump is situated on top of the water tank)

[Tony Brooks]

58 minutes ago, Alan de Enfield said:

 

Absolutely - unless the pump is above the tank water level.

(My pump is situated on top of the water tank)

 

Er, the pump valves allow flow from the tank to the system, I think there is every chance that if the main pipework was below the tank level, and it sprung a leak it would syphon. I would not rely upon six little rubber valves to seal in the direction they are supposed to allow flow.

 

If the pump started leaking then I agree air would enter the leak   rather the water come out, but then the valves (two per pumping chamber) would be trying to stop any water in the pump  d raining back into the tank, but that won't be a lot.

[Tracy D'arth]

A spring non return valve in the outlet of the pump may stop it syphoning but it would have to be before the accumulator especially if there is no expansion vessel on the hot water system.