Horizontal Cylinders...Good? Bad? Ugly?

My customer has a system boiler and unvented 170litre (upright) cylinder in their loft. Adding an extension to the house, including a bathroom, they want to increase the cylinder capacity (I don't think there are any additional occupants being added, but they want to 'future-proof'). They'll also upgrade the boiler.

Loft hatch is 60cm x 60cm, so will take up to a 55cm dia cylinder (same as existing) as long as there are no welded feet/stands/other protrusions which add to that diameter (naturally fittings will be added in situ). Vertical installation space is limited, so I am considering a horizontal cylinder (I've seen a Gledhill one, maybe others?) up to 250litres, which will be 175cm in length. Note: I believe(!) there is sufficient room to insert a 175cm long cylinder into the loft (but not to install that height in the required location)...I will do a little more verification on this, though. I'm keen to continue to use the loft space, given that all the plumbing is already there, and it's a good use of the space.

I've not fitted a horizontal cylinder before, and haven't really heard anything about them. So, I'd like to canvass opinion here, ideally from your practical experiences...pros and cons, warnings, etc, including whether Gledhill is OK (my experience is limited to Megaflos).

Much obliged.

https://mcdonaldwaterstorage.com/contact/

Call the tech team on this link, they are excellent and will talk through everything with you, I have used them loads , you dont have to buy from them, I usually do as they will make any dimension cylinder you want, and are very competative, the tech guys are very friendly and knowledgeable

Take longer to heat up (poorer convection current set-up) and have less "working volume" as there is much more volume below the lowest level of the heating coil. You can cater for that by over-sizing. Advantage - weight of the cylinder+ water can be spread across more joists (assuming you fit it perpendicular to the joists).

Nozzle

Nozzle said:

Take longer to heat up (poorer convection current set-up) and have less "working volume" as there is much more volume below the lowest level of the heating coil. You can cater for that by over-sizing. Advantage - weight of the cylinder+ water can be spread across more joists (assuming you fit it perpendicular to the joists).

Nozzle

Click to expand...

You can overcome that by fitting a destrat pump.

Stay vertical if you can. If you've got 60cm clear width through the hatch, use it. Joule do a 60cm wide cylinder, the 200L version is shorter than a standard diameter 170L, and the 250L is only 90mm taller. Fit it with hot water priority though and the 200L will be more than they ever need. Remember 200L stored is about 300L at bath temperature. That's enough to fill three baths.

Appreciate all those replies, really useful. I'll certainly talk to McDonald WS - always happy to take expert input. I'll re-check the hatch size... 60cm could be very snug (probably won't have any paint left on it by the time I've got it up there . Thanks again.