How do I identify header tanks of reliable quality?

[GNNMartin]

A black plastic cold water header tank has split in our roofspace, and we need to instal a replacement. I want to ensure if possible that the replacement is of good quality.

The failing tank is one of two, each of capacity 25 gallons, ganged together. The replacements will have to be 2 coffin tanks ganged together if we are to get them into the roofspace through the existing access. We decided to replace both tanks, reckoning if one has split the other is unreliable.

We had the failing tank installed as part of major building work about 23 years ago. I feel we were unlucky or had a poor quality tanks installed: I would not expect a black plastic tank to fail so quickly.

1: Who can be relied on to supply a tank of good quality?
2: How long (as a minimum) should a tank be expected to last?

I am inclined to buy a Polytank tank, since that is the only one I can find for which I can find information about the manufacturer. However, if anyone here has advice I will be grateful to receive it.

 

[Rickster123]

It's failed after 23 years and you think you're unlucky? Send it back with a strongly worded letter...:devilish:

 

[SimonG]

Go to merchants.
Stick tank on head.
No sign of daylight?

It'll do lad.

 

[Best]

I would like to hope a cold water tank would last at least 40 or 50 years and some will.
But a lot of these rectangular tanks are not brilliant and also are subject to stress due to their design. A round plastic tank is the best because it has no weak points, but won't do most situations.
Make sure any new tank you buy has not been scraped along a concrete floor on its base.
Better in my opinion if having 2 cold tanks, to keep each separate with a ballvalve on each - one tank for cold supplies, other for supply to hot cylinder. That way there's no connecting pipe which can sometimes cause stress on tanks.
Make sure they have a strong flat level base and no woodworm about as they are a risk to tank

 

[snowhead]

Where has the tank failed?

If it's around a hole drilled , or burned thro', during installation, then it's not the tanks fault.

As Best said, if it's been mishandled before and or during installation, it's not the tanks fault

Has it ever frozen?
Has it ever been subjected to hot water?
Does it get hot in the roof space?
Does it sit on a strong base?
Has anyone done any other work in the roof space aver the years?

All the above matter as the same could happen to the replacement.

 

[Best]

As above, ^^^ If the base is twisted out of shape it will let the tank twist out of shape & stress it. Same with the much thicker skinned oil tanks if they are not fitted properly.
That said, I did see a rectangular tank similar to the latest type, but probably about 30 years old and it had suddenly leaked from the corner where the plastic where the tank narrows. That point would be stretched and strained because the sides try to push out with the water. That was therefore due to just bad design and age.

 

[GNNMartin]

Thanks to both for your advice. The tank split at the base. The split runs across the base from the edge inwards. I assume that the split is at a weld, but can't actually see that until we get the tank out. Are tanks made from parts welded together, or are they made in one piece? The tank has never frozen, and has not received any hot water (at least, not enough for us to notice). The roofspace gets warm as roofspaces do, but it is a North facing roof slope, so I don't think it gets unduly warm. No noticeable signs of damage, and a firm level blockboard base. No other work in the roofspace, other than swapping the ball valve a couple of times, and attention to the ball valve a few times as it became apparent that it was necessary to replace it.

We assumed the tanks were put in during the building, because they couldn't be put in through the opening that gives access now. I suppose it is conceivable that they were distorted to get them in through the current opening. That seems unlikely, since I would not expect that they could be distorted enough: on the other hand, if they were, than perhaps that is the cause.

The main problem at the moment is getting a plumber who is not too busy to take on the job. I won’t actually take any decisions until we find a plumber and can get his advice. I’m a bit happier now that I've found tanks that come from a named manufacturer who has a web site and a history. Currently looking at tanks by Ferham or Polytank. Any comments on these manufacturers?

Interesting suggestion to have one tank feeding the cold water and one feeding the hot water tanks. I don’t think we will go with that for a few reasons. First the failure was nowhere near the point of entry of the pipe joining the two tanks. Second, it requires quite a bit of replumbing elsewhere in the house. Third, we have pumped showers which are currently very satisfactory, but the installation advice says that the hot and cold supply should be taken from a point which ensures that viscous and header imbalances are minimised. If all the water for the shower is taken from one tank, it could more easily empty the tank. If the cold is taken from one tank and the hot from the other, then the balance could be badly affected by (say) a dishwasher and/or a washing machine and/or lavatory drawing water. The showers were not very good to begin with because the plumber ignored the installation advice: the pipe runs were reworked, but it indicates the potential for getting things wrong! Also, our son used to take showers so long that he emptied both tanks, whereupon the shower suddenly delivered very hot water. He’s left home now, but I don’t want to decrease the safe duration of a shower by feeding the shower from a single tank.

 

[Stigster]

If it is installed correctly then burning shouldn't be an issue. The cold feed to the hot water cylinder should be higher than the cold feed to the outlets. This is so that in the case of the tank running down low, the hot will stop and it will only deliver cold. Both ways can be compliant if installed properly.

 

[AWheating]

Holes should not be burnt/ melted through a plastic tank. First things first is the tank stand built properly? It needs to be bigger than the tanks and very strong to fully support the tank so it's not stressed at its base.

If you wanted stronger tanks maybe copper or fibreglass?

 

[SimonG]

Light bulb near tank?

Halogen spotlights under tank?

 

[Ray Stafford]

Currently looking at tanks by Ferham or Polytank. Any comments on these manufacturers?

They are both well established, reputable manufacturers.

If you wanted to look at alternatives, you might try Sarena Plastics, but expect to pay more money.

 

[Best]

Thanks to both for your advice. The tank split at the base. The split runs across the base from the edge inwards. I assume that the split is at a weld, but can't actually see that until we get the tank out. Are tanks made from parts welded together, or are they made in one piece? The tank has never frozen, and has not received any hot water (at least, not enough for us to notice). The roofspace gets warm as roofspaces do, but it is a North facing roof slope, so I don't think it gets unduly warm. No noticeable signs of damage, and a firm level blockboard base. No other work in the roofspace, other than swapping the ball valve a couple of times, and attention to the ball valve a few times as it became apparent that it was necessary to replace it.

We assumed the tanks were put in during the building, because they couldn't be put in through the opening that gives access now. I suppose it is conceivable that they were distorted to get them in through the current opening. That seems unlikely, since I would not expect that they could be distorted enough: on the other hand, if they were, than perhaps that is the cause.

The main problem at the moment is getting a plumber who is not too busy to take on the job. I won’t actually take any decisions until we find a plumber and can get his advice. I’m a bit happier now that I've found tanks that come from a named manufacturer who has a web site and a history. Currently looking at tanks by Ferham or Polytank. Any comments on these manufacturers?

Interesting suggestion to have one tank feeding the cold water and one feeding the hot water tanks. I don’t think we will go with that for a few reasons. First the failure was nowhere near the point of entry of the pipe joining the two tanks. Second, it requires quite a bit of replumbing elsewhere in the house. Third, we have pumped showers which are currently very satisfactory, but the installation advice says that the hot and cold supply should be taken from a point which ensures that viscous and header imbalances are minimised. If all the water for the shower is taken from one tank, it could more easily empty the tank. If the cold is taken from one tank and the hot from the other, then the balance could be badly affected by (say) a dishwasher and/or a washing machine and/or lavatory drawing water. The showers were not very good to begin with because the plumber ignored the installation advice: the pipe runs were reworked, but it indicates the potential for getting things wrong! Also, our son used to take showers so long that he emptied both tanks, whereupon the shower suddenly delivered very hot water. He’s left home now, but I don’t want to decrease the safe duration of a shower by feeding the shower from a single tank.

Plastic tanks are made in one piece and not welded.
I would examine the support base that your tank sat on and check if it is level and no dips on it. If it had a dip in one corner, for example, it would mean the base is getting bent.
Frankly, rectangular cwts are not a lifetime item by their design as well as the material & its thickness. Plastic stretches until it cracks eventually, or if it can't stretch it will often crack sooner, - that's plastic for you!
I tend to recommend anyone doing a bit of replumbing in their home to just replace the cwt if it has a few years on it, or looks poor in any way. Not big money for a plastic cwt.
As to your point about not liking the idea of one tank for one supply, - I take your point.
But it is highly unlikely large draw off taps or mixers (bath or showers) would only be using solely one water and not mixed water, so therefore both tanks will be drawn from. That's unless someone likes ice cold showers or 40 degree scalding showers. Even at 40 degree, the water will normally be from both cold & hot supplies to bring it down to that.
The head height will not be affected by separate tanks varying draw offs and is not what the manufactor meant by same head supplies. They are no doubt referring to cold tanks fitted at different levels, - different floors for example.