Reroute ductwork for larger cold water storage tank?

[BenjyK]

I’m looking to install a pump (Stuart Turner Monsoon or Salamander) to boost hot water pressure all around a 3-bed maisonette, which is very poor currently. The pump manufacturer specifies a minimum of 50 gallons cold water storage for a single bathroomed house, which would mean having to get a larger tank.


The issue is I don’t have space for that in my airing cupboard unless I reroute a short section of ducting that’s in the way. The ducting is connected to a circular diffuser in the bathroom then runs across the airing cupboard (135cm wide), disappearing into a wall off to a central extraction system on the roof that is shared by the whole block. The ductwork is circular and roughly 110mm.


I’m thinking of rerouting the ducting up over the new tank and back down again to where it disappears into the wall, using 100mm ductwork and some kind of adapter back into the 110mm. However, my worry is this will ruin the airflow with adding four extra bends in the run. Is this a genuine concern?


Also, is a 50 gallon tank really that necessary, or is the manufacture just trying to cover all bases?


Thanks!

 

[cross thread]

Yes you do need the capacity, can you fit another tank side by side to give the capacity you need

 

[gasbanni]

What's your cold pressure like if it's good ....Forget pumps !

I suspect you'd be better with an unvented cylinder or a thermal store. Your poor hot water pressure is simply due to the lack 'head ' from you storage tank feeding the cylinder .....an easy fix done properly !

 

[BenjyK]

@gasbanni cold pressure from the mains is just fine. Both unvented cylinder or thermal store sound like quite expensive options? It's not something I know much about, but wouldn't I need to get a system boiler installed with an unvented cylinder...

A pump seems like it may well be the most straightforward option without having to overhaul too much of the system. To meet the cold water capacity requirement I've been looking at bespoke tanks to make the most of the space in the airing cupboard, as I don't fancy messing with the ducting. None of the standard tank sizes will fit unfortunately.

 

[oldbutnotdead]

Swapping an existing vented cylinder for unvented isn't DIY but shouldn't break the bank either. If your existing cylinder is heated by your boiler then the new unvented can be heated by the boiler. The cylinder coil is just a thermal load as far as the boiler is concerned.

 

[gasbanni]

@gasbanni cold pressure from the mains is just fine. Both unvented cylinder or thermal store sound like quite expensive options? It's not something I know much about, but wouldn't I need to get a system boiler installed with an unvented cylinder...

A pump seems like it may well be the most straightforward option without having to overhaul too much of the system. To meet the cold water capacity requirement I've been looking at bespoke tanks to make the most of the space in the airing cupboard, as I don't fancy messing with the ducting. None of the standard tank sizes will fit unfortunately.

Installing pumps enlarging the header tank .....its all a carry on. Honestly the easiest way is to fit an unvented by the time you've compared things it's probably the cheapest easiest option. Or just get a combi boiler fitted. With a combi you have unlimited hot water at a good pressure. With any stored hot water system you can fun out of hot water. I wouldn't even bother quoting for the work your proposing ........it really isn't the answer.

Obviously a site inspection would give all the info for a good solution. I suspect you can carry on as you think and may not be happy with the end result and it may end up costing you more than just having a combi fitted !!!!

 

[BenjyK]

I appreciate all the input! Thanks to your comments I've pretty much decided not to go for a bigger cold tank and the pump and go for an unvented cylinder instead.

The remaining issue I have is identifying what the pipes are feeding the airing cupboard. We're not sure if the cold feed is off the mains, or a communal tank on the roof. I'm trying to get access to the roof through the managing agent, but might not be able to. They have not been at all helpful so far.

Whatever the pipe is... the pressure is very good and a lot higher than what we get in the kitchen. So I'm wondering if the airing cupboard is fed from a tank on the roof and the kitchen is directly from the mains.

In terms of the unvented cylinder, does it have to be from the mains or can it be gravity fed if the pressure is good enough?

 

[BenjyK]

I spoke to Joule who told me it has to be mains fed - "An unvented cylinder needs to have a constant pressure and supply and you would not have this on an unvented cylinder"

I have to admit I still don't fully understand why it can't be gravity fed if the pressure is more than adequate... in the meantime, I'll keep on at the managing agents to try and get access for pipe tracing!