Welding an aluminium water tank

[jeremyshaw]

I have an aluminium water tank.

On a recent delivery trip the crew reported that there was air in the water supply. They traced all the lines back, tightened up where appropriate, but it continued.

A few days later the water supply failed. The pump sucked dry despite the tank being nearly full. The pump was happy with an alternative supply, so the pump is good.

We concluded that the lift pipe must have fractured, probably at the joint at the top of the tank. Maybe years of water sloshing around have stressed it. They had some rough weather. There is no inspection hatch to check.

I plan to remove the tank, and install an inspection hatch, but have little knowledge of welding aluminium. Do you think it will be possible to get an aluminium welder to fix it, or would the lift pipe have been welded in before the tank was made up, making it very hard to do? As far as I can see you'd have to cut out the connector, make a new pipe with a flange and weld the flange to the top. I am wondering about just using a plastic tank connector instead, especially as I may find it difficult to find an aluminium welder while the boat is in Morocco.

Any advice would be appreciated. Thanks.

 

[Neil]

HTS-2000 aluminium brazing rods should do the trick - and it should be a DIY job. I bought some myself, but haven't actually used them yet, so I can't comment, but the videos make it look easy. Check here for details:

http://www.aluminumrepair.com/aluminum_repair.asp

 

[PCUK]

Use a tank connector from the plumbers and make up a lift pipe with copper tube. Hence no welding!

 

[earlybird]

HTS-2000 aluminium brazing rods should do the trick - and it should be a DIY job. I bought some myself, but haven't actually used them yet, so I can't comment, but the videos make it look easy. Check here for details:

http://www.aluminumrepair.com/aluminum_repair.asp

Sales videos always make the job look easy.
Aluminium welding can be tricky. Its high thermal conductivity and low melting point readily result in large holes rather than a proper joint, particularly in sheet material.
I think the OP needs a skilled welder, preferably with AC TIG kit.
Otherwise go for a mechanical joint repair.
Add:- I think I'd be cautious about a copper connector as suggested above. Plastic would be a better choice IMHO.

 

[alexrunic]

I would not use the brazing rods as suggested the quality of the repair will be very poor. if you cant affect a mechanical repair find a GOOD ali welder hopefully one recommended to you.

 

[PCUK]

Why don't you like copper Early bird? It's used for all domestic systems. Please don't say corrosion!!!

 

[Neil]

Sales videos always make the job look easy.
Aluminium welding can be tricky. Its high thermal conductivity and low melting point readily result in large holes rather than a proper joint, particularly in sheet material.

Well, the repair of a hole in an aluminium drink can looked authentic. The whole point is that the alloy rods melt at much lower temperatures than the actual aluminium substrate, therefore no holes - remember, the rods melt at propane blow torch temperatures....did you look at the videos?

Though without personal experience, I'd like to hear of a user's direct knowledge to the contrary.

 

[2Tizwoz]

You need a good welder used to welding aluminium for the reasons which earlybird has described.

If you decide to repair rather than replace the pipe, as water is involved it would no doubt be better to have it welded using aluminium thus avoiding dissimilar metals giving potential corrosion problems.

Your plan to cut an access hatch and install a plastic connector looks like the best option both for now and future maintenance.

If you drill and tap the tank to take some M6 aluminium bolts which you can screw in from the inside of the tank the nuts and access plate can be removed in the future.

 

[earlybird]

Why don't you like copper Early bird? It's used for all domestic systems. Please don't say corrosion!!!

I must say corrosion!!! Domestic systems don't usually have aluminium components and I'd have thought the combination was very prone to galvanic corrosion in the mid to long term.
May be wrong, but I'd prefer to avoid the risk unless convinced otherwise.

 

[Neil]

You need a good welder used to welding aluminium for the reasons which earlybird has described.

Why don't you just watch:

http://www.aluminumrepair.com/video_new.asp , then tell me why it wouldn't work

The video has 3 or 4 different types of repair on aluminium water tanks

 

[earlybird]

The whole point is that the alloy rods melt at much lower temperatures than the actual aluminium substrate, therefore no holes - remember, the rods melt at propane blow torch temperatures....did you look at the videos?

Though without personal experience, I'd like to hear of a user's direct knowledge to the contrary.

I've looked at the video and can only say that I find it very surprising. One of several major difficulties with aluminium joining is the tenacious oxide film that forms very readily.
This technique seems to magically avoid this, even takes dirt in its stride.
Also, the molten metal's ability to bridge sizeable holes seems a bit hard to credit, but maybe it's all true!!
Can you report on your purchase when you've tried it. I'm willing to be conviced.

 

[2Tizwoz]

Why don't you just watch:

http://www.aluminumrepair.com/video_new.asp , then tell me why it wouldn't work

The video has 3 or 4 different types of repair on aluminium water tanks

It may well work mechanically but the metal used appears to be zinc so may suffer from corrosion problems.

 

[jeremyshaw]

Many thanks for all the replies. I'm pretty uncertain about finding a decent aluminium welder in Morocco, though I'm sure they exist, so I think I'll try a DIY job with a plastic tank connector.