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Horizontal hot water cylinders

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Horizontal hot water cylinders

Bespoke open vented horizontal hot water cylinders

Index Page > Hot Water Cylinders > Horizontal hot water cylinders

Direct and Indirect horizontal vented hot water cylinders

Can be built to your specification. Supplied as direct or indirect patterns and complete with cradles.


So what's the difference?

Horizontal cylinders differ greatly from their vertical counterparts. For example, a vertical cylinder has a convex top and a concave base. When a cylinder is manufactured to lay on it's side so to speak it is manufactured with two convex ends.


Connections on a horizontal hot water cylinder.

Everything about a horizontal hot water cylinder differs to the vertical counterpart. Vertical cylinders tend to have the cold water feed on the side at the bottom with the hot water draw off in the middle of the dome at the very top. Because the domes on a horizontal cylinder are not at the top the location of these tappings also needs to be repositioned accordingly.


Horizontal hot water cylinder with cradles

Above: Typical horizontal hot water

 cylinder with support cradles


The cold inlet on a horizontal cylinder is normally positioned on the bottom of the vessel at one end.


The hot water draw-off is usually on the top of the vessel at the opposite end to the cold water inlet.


A horizontal cylinder requires support.

The cylinder cannot just lay on it's side on the floor, it requires support. For this reason, horizontal cylinders can be supplied with a steel cradle. The cradle also stops the cylinder from moving - a full cylinder becomes very heavy! You are of course at liberty to devise or make your own support.  Factory cradles hold the cylinder approximately 100mm above the surface upon which it is supported, so remember to factor this into any measurements. (i.e. Cylinder diameter + insulation thickness + 100mm cradle height)


A slight slope

A horizontal cylinder should be installed with a slight slope up towards the hot water draw off point. This encourages air bubbles to work their way toward the vent, preventing the build-up of an air pocket along the upper edge.


Boiler connections on an indirect horizontal hot water cylinder

Connections and internals on a horizontal cylinder are very different to those found on a standard vertical hot water cylinder. To illustrate this point, consider laying a vertical indirect cylinder on it's side. The boiler water that was previously travelled in a descending coil would now be effectively travelling in a rising and falling motion - and near to one end only. This would cause many problems and would not work efficiently. So in a horizontal cylinder the heater exchanger (boiler coil) is modified to travel along the lowest part of the cylinder (in the coolest water) from one end to the other. The boiler 'flow' is fed in through the top of the cylinder, down to the heat exchanger at one end and returns to the boiler through the bottom of the cylinder at the other end.

Horizontal hot water cylinder diagram showing typical layout, support craddles and route of boiler heat exchanger

The cold water feed to the cylinder is typically on the underside of the cylinder below the point where the boiler flow connects and the hot water draw-off in on top of the cylinder above the boil return (as is the vent connection and shower take-off if required).


A tapping for a drain is often considered a good idea and can be incorporated on the lower side (bottom) of the cylinder body.


Horizontal hot water cylinders with immersion heaters

Horizontal hot water cylinders can be fitted with immersion heaters just like a vertical cylinder might. However, to keep the element/s as low in the cylinder as possible it is preferable to have immersion heaters fitted in the end/s of the cylinder.


Horizontal hot water cylinder and shower take-offs

A shower take-off can be fitted to a horizontal hot water cylinder. The purpose of a dedicated shower take-off is to draw hot water from a level just below the top of the cylinder. In doing so air bubbles (which naturally rise to the top) are prevented in the main from entering this dedicated feed to a shower booster pump and negate problems one might experience without such a fitting such as cavitation. (Ordinarily you would need to purchase a device known as a 'Surrey Flange' to do such a job at extra cost.)


Horizontal cylinder fed by an 'unpumped' heat source.

It is possible to heat a horizontal cylinder with an unpumped heat source such as a wood burning stove or an AGA. Unlike the heat in a typical household system in which hot water from a normal gas or oil boiler is moved by a small circulating pump, unpumped heat sources (as their name suggests) do not utilise a pump in order to circulate water on their route to dump heat, instead they rely on what's known as thermosiphoning - a gravity flow created by the action of warm water rising and cooler water falling.


To explain further, water heated by the appliance (AGA, Rayburn, woodburner, etc) is hotter than water returning from the cylinder, so when pipework is configured correctly hot water will rise to the cylinder, give up its energy, then return to the heating appliance as cooler water for the cycle to repeat itself - a circulating flow being created. This is an 'age old' and very simple principle which is quite effective. You will however need a larger bore heat exchanger in the cylinder than the type used in a fully pumped system to ensure a good flow of water for this gravity principle to work well. Do not use a cylinder designed for a pumped heat source on a system relying on gravity circulation.


Horizontal hot water cylinder with gravity boiler coil.

Horizontal cylinders can be made with a gravity coil (for an unpumped heat source), but you must specify this requirement. Failure to do so will result in you receiving a standard cylinder suitable for use on a pumped system. A gravity boiler coil is a little more expensive than a pumped coil for the simple reason it is larger. Please refer to price tables.


Options for fittings. We can supply your cylinder with various types of connections depending on your requirement and preference. We can also configure your cylinder with the tappings (connections) in positions that best suit your installation. If you have special requirement you are welcome to call and discuss your installation before making purchase to ensure we arrive at the best possible solution.



Frequently Asked Question

Q. Can you supply a horizontal unvented cylinder to provide mains pressure hot water?

A. Yes. We are able to supply mains pressure horizontal hot water cylinders manufactured from either Stainless Steel or heavy grade Copper. Please call for advice.



Cylinder price includes high performance insulation, an immersion boss (heater is an optional extra) and all required tappings and connections. For additions and extras please see table below. Cylinders are manufactured to a horizontal pattern.


Cylinder Size

(Excluding thickness of Insulation)

Capacity Imperial Size inc VAT  
750 x 400 82 30 x 16 456.33  
825 x 400 91 33 x 16 490.78  
900 x 400 98 36 x 16 458.56  
1050 x 400 116 42 x 16 475.56  
1200 x 400 136 48 x 16 499.58  
1500 x 400 170 60 x 16 532.83  
675 x 450 89 26 x 18 457.94  
750 x 450 98 30 x 18 467.94  
825 x 450 111 33 x 18 497.93  
900 x 450 120 36 x 18 438.43  
1050 x 450 144 42 x 18 469.24  
1200 x 450 166 48 x 18 492.39  
1500 x 450 222 60 x 18 548.57  
1800 x 450 268 72 x 18




*When describing the size of a cylinder it is customary not to include the insulation in the measurement. The cylinder will be supplied insulated (in compliance with Part L of the Building Regulations), but with the various choices of thickness you can opt for things would get very complicated if insulation were to be included in the stated size. For this reason only the dimension of the bare copper cylinder is mentioned. So, be aware that the final size of the cylinder supplied will be in excess of quoted dimensions. Ensure you have enough space.


Cylinder price includes high performance insulation, an immersion boss (heater is an optional extra) and all required tappings and connections. For additions and extras please see table below. Cylinders are manufactured to a horizontal pattern.

Cylinder Size

(Excluding thickness of Insulation)

Capacity Imperial Size


    inc VAT  
750 x 400 82 30 x 16 441.22  
825 x 400 91 33 x 16 465.78  
900 x 400 98 36 x 16 413.56  
1050 x 400 116 42 x 16 425.33  
1200 x 400 136 48 x 16 451.58  
1500 x 400 170 60 x 16 517.83  
675 x 450 89 26 x 18 382.94  
750 x 450 98 30 x 18 382.94  
825 x 450 111 33 x 18 412.93  
900 x 450 120 36 x 18 418.43  
1050 x 450 144 42 x 18 429.24  
1200 x 450 166 48 x 18 472.39  
1500 x 450 222 60 x 18 529.75  
1800 x 450 268 72 x 18 680.78  

Additions and optional extras

Supports for horizontal cylinders


Horizontal cylinders require support. You can make support frames or cradles to suit, or you can purchase the factory option cradles from the following list:


Support cradles 900 to 1200 cylinder



Support cradles over 1200 cylinder



Options available at additional cost include:


Compression fittings (instead of threaded bosses)



Shower take-off



Additional Tappings (pairs)



Secondary return



Immersion Heater (Incalloy) 3kW alloy coated (corrosion resistant)



Drain valve (drain cock) [threaded boss included on cylinder]



Enhanced insulation (approx 75mm)*

(heat loss figures available on request)



Super thick insulation (approx 100mm)*



Hi recovery boiler coil (pumped)



Additional immersion boss (supplied with one)



Gravity boiler coil with 28mm connections (Large bore AGA)


(please add to stated price)


Additional boiler coil (making it a twin coil unit)



Solar Coil


Positioning tappings to your specification does not normally attract a supplementary charge


*When enhancing the thickness of insulation remember the impact this will have on the over all finished size. Please ensure the additional size does not compromise your ability to get the cylinder through any access opens, such as a loft hatch or doorway and still gives enough room to make necessary connections.

Illustrations are for guidance only, not to scale and should not be interpreted as an exact representation.


For more info please call


Horizontal hot water cylinder




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