Height of CWS tank above cylinder in loft

[Megahertz]

Hi guys, I'm looking for some reassurance I think with this one!

I'm in the process of upgrading cylinder, cws tank, and have just installed a brand new 100gallon polytank in the loft, and am intending to put the cylinder underneath when it arrives on Tuesday.

The tank is right up into the eaves, although the highest I can get it is 205 cm above the floor of the loft. I realise that shouldn't be a problem, except that the cylinder is 202cm tall! This means that, once I put the cylinder on a sheet of 12mm ply, and put the pipes in the top, the top of the cylinder will be about level with (or only just below) the bottom of the water storage tank.

I'm installing a Salamander whole house pump, so I'm not expecting any problems with water pressure at the taps, but will the fact that the top of the cylinder is level with the top of the bottom of the tank cause any problems? For example, if the water level drops in the tank, will I get air sucked into the pump through the vent?

All I can find in terms of information is that the bottom of the tank needs to be 2 metres above the bottom of the cylinder, which it is - it's just that it's a very tall cylinder!

Any help would be appreciated!

 

[Dan Robinson]

Should be fine as long as you use the appropriate flange.

 

[Agile]

Well at least Dan is happy!

But I would want to see at leat 1 m between the top of the cylinder and the bottom of the tank.

I would also expect 28 mm or larger tube connecting the two.

Presumably the pump is going to be between the tank and cylinder? In that case as long as it starts reliably there should be no problem!

However, to protect the pump against starvation, I would be inclined to fit a level switch in the tank to disable the pump if the tank level fell too low.

Tony

 

[Megahertz]

Thanks both for the replies.

Actually, I've gone for an open vented cylinder, and the pump is going AFTER the cylinder.

I'm slightly concerned that if the water in the tank drops too far, then the water in the vent pipe will also be low, and this might mean air being sucked into the pump.

I'm going to fit one of these http://www.screwfix.com/p/salamander-s-flange-22mm/76906 these on the top of the cylinder which will mean that the outlet should be 50mm lower, but it is going to be tight.

I think my options are:-

Try to negotiate a slightly smaller cylinder (250l as opposed to 300l) although it's been on order for a while and arriving on tuesday so this could be awkward!

Put the new cylinder in the airing cupboard on the first floor where the old one is (I really don't want to do this if I can help it)

Continue as planned and cross fingers!

The idea of a level switch is a good one - this would in effect switch off the hot and cold water until the tank fills up again? I'm not sure if the pump (Salamander RHP100) will allow water to flow through if there's no power to it?[/url]

 

[seco services]

Don't put the pump on the same pipe as the vent it needs to be seperate ie on a flange.
You'll draw air in to the pump otherwise.

 

[Agile]

I cannot help thinking that you are going to have problems!

You have virtually no head of water between the tank and cylinder yet the pump will be drawing out say 10-20 li/min ( which your gravity feed will not provide in my view! )

Are you still happy Dan?

Tony Glazier

 

[Megahertz]

Thanks all for the advice

I had a little trouble posting the link to the flange I'll be using but it's here

http://www.screwfix.com/p/salamander-s-flange-22mm/76906

The supply to the pump will be from the special outlet from the flange, and I'll take the vent pipe up from the normal outlet from the top of the cylinder.

The pump will be at the base of the cylinder so there will be at least 2 metres head on the pump inputs. And of course I'll use 28mm pipe between the CWS tank and the bottom of the cylinder.

Thanks again

 

[Dan Robinson]

Tony - With the appropriate flange, and 28mm feeds... yes.

I will add a caveat in that the OP hasn't said how big the CWS cistern is.

A float switch is a good idea though if only to protect the pump.

The main consideration is the height of the highest outlet and the pump. If the pump is on the deck next to the cylinder, and the correct flange is used, then I fail to see how air will be a problem. Salamander state 600mm minimum head.

 

[seco services]

OP hasn't said how big the CWS cistern is.

100 gal

 

[Dan Robinson]

Just testing .

 

[steve32]

It would have been better to fit a horizontal cylinder

http://www.discountedheating.co.uk/shop/acatalog/Newark_Standard_Horizontal_Cylinders.html

 

[Dan Robinson]

They are the spawn of Satan those things. Possibly the worst way to heat, store and distribute hot water.

 

[Agile]

Tony - With the appropriate flange, and 28mm feeds... yes.

I will add a caveat in that the OP hasn't said how big the CWS cistern is.

A float switch is a good idea though if only to protect the pump.

I dont see the size of cistern as very relevant!

Only the refill rate compared with the useage rate.

However large the cistern is, it will eventually be emptied if the refill does not exceed the discharge rate.

At that point my level switch will come into its own!

Tony

 

[Dan Robinson]

Because it is usually easier to sort out an undersized cistern than it is the fill rate.

No need to over think things Tony .

 

[Agile]

I start any planning work with a thorough set of measurements of everything which could ever be involved.

An oversize float valve or two in parallel can work wonders at significantly increasing the refill rate.

Tony