Replacing F&E tank in loft

[bloxy]

I have an oil fired Trianco boiler, the feed and vent come directly off one side of the boiler and the 28mm flow and return come off the other side of the boiler. Pump is in the return. System is microbore with two manifolds and a feed to the HW cylinder (open vented indirect HW) each of those three circuits is controlled by its own two port valve.

The F&E tank in the loft is right up in the apex of the roof well above the level of the outlet of the cold water tank which it's self is raised off the loft floor by 2.5 feet ( and which I replaced last year with a modern water bylaw one). The F&E tank is uncovered and uninsulated and rather flimsy. The vent pipe only sits on the edge of the tank it does not rise any sort of height above it before descending down.

I am replacing some downstairs rads so since I have to do the complete drain down of the descending loops, I am going to take the opportunity to replace the tank as well for a more suitable one.

So advise required on location and heigh please.
1. Should I position the new tank below the cold water storage tank or at the same level?
2. Is the a calculation as to what height the tank should be at?
3. How high should the inverted U of vent pipe go before descending back down?

Thanks for any help.[/list]

 

[doitall]

One could assume it was put at that height for a reason, so you certainly shouldn't lower it.

It the pump is on the return there would be a good chance of blowing over the vent, which should be as high as possible before dropping down, there is a calc, but if it works ok leave it where it is.

You can buy a bi-law kit for the tank to lag it with.

 

[bloxy]

One could assume it was put at that height for a reason, so you certainly shouldn't lower it.

Not so sure it was a good install in the first place (1970s). Lots of stuff in the building is odd. Like: The motorised valves are under the toilet floor! Really convenient when the valve goes, which they do every year or two presumably because they are so hot sat next to the manifolds. So I wouldn't be surprised if they put the tank there because it was easy to nail a couple of short bits of 3x2 between the rafters and stick a piece of chip board on top for the tank to sit on.

I thought you were not supposed to have the F&E tank above the cold water storage tank in case of pin holing in the HW coil? That happened when we first moved in 20 odd years ago, ran a hot foamy bath of Fernox, nice!

The other reason for moving it is it is right above the loft hatch so I bash me head on it every time I go up there

 

[doitall]

I gave you a straight forward answer to your question.

If you want to move the cold feed and vent and re-pipe to today's standards then that's a different kettle of fish altogether.

In the interim lower it if you want the extra work, but you will be putting it back where it is, that I will guarantee. Or at least the same height.

 

[bloxy]

I gave you a straight forward answer to your question.

Thanks

If you want to move the cold feed and vent and re-pipe to today's standards then that's a different kettle of fish altogether.

Yes, as I intended to re-site it I was to do it with a tank to current standards. Re-doing the loft pipe work is not a problem.

In the interim lower it if you want the extra work, but you will be putting it back where it is, that I will guarantee. Or at least the same height.

I can put it at the same height as now just in a more convenient position at the gable end but I was concerned it was at the wrong height originally and that is why I thought it should be lower.

 

[doitall]

In an ideal world, the two water levels would be the same, in practice they hardly ever were.

As said it was put at that height to prevent circulation problems from a low head.

 

[bloxy]

As said it was put at that height to prevent circulation problems from a low head.

Is that because with the pump on the return it tends to suck water back down the feed and vent pipes?

 

[doitall]

Sort of, it means you have a negative pressure on the system and a positive pressure on the vent.

 

[bloxy]

So the tank would be so high to prevent pumping over on the vent and to give enough head for the negative pressure on the feed?

Also explains why my bathroom rad is always needing bleeding, negative pressure in system must be sucking in air somewhere.

 

[doitall]

That could be a blocked cold feed, check the tank and clean before you drain down.

Hold a glass under the vent pipe and get someone to turn the heating on, does it suck the water out of the glass.