Combination cylinder pump for low hot water pressure

[st07]

Hi,

My mum lives in a flat where the hot water is supplied from a vented combination cylinder. As you probably know the hot water pressure is very very low in this situation and as I understand it the only ways of boosting pressure are either a) raise the height of the tank or b) use an electric pump on the hot pipe. Raising the tank just isn't possible so I'm thinking of installing a pump.

The hot pipe comes in 22mm from the tank to the bathroom where it feeds the bath tap. Here it also it splits to a 15mm pipe that goes to both the kitchen sink tap and bathroom sink tap. With this in mind, I have a few questions I'd be grateful if anyone could answer.

Most pumps I notice come with 15mm push-fit connections. As the initial feed from the tank is 22mm I guess I'll need 22mm fittings. Would a pump like this one plus these fittings do the job? : http://www.ebay.co.uk/itm/STUART-TURNER-Showermate-Eco-2-0-Bar-Shower-Pump-SINGLE-/310232055691?

http://www.ebay.co.uk/itm/Speedfit-Flexible-Tap-Connector-22mm-x-3-4-300mm-/260987184655

Also, is there any risk of emptying the tank too quickly, the pump sucking in air and/or damaging it by doing so? As the hot pipe is side entry I guess there's no such thing as a surrey flange needed?

http://www.simplifydiy.com/plumbing-and-heating/hot-water-storage/combination-vented

Thanks in advance

 

[Dan Robinson]

Probably better to have it removed and replaced with an unvented cylinder.

 

[st07]

To be honest, the low pressure isn't a huge deal. Her shower is electric and that's what gets used most - baths are rare. I've read about unvented cylinders, they're pretty expensive and need maintenance every year so the costs are adding up. I thought a small electric pump would be a cheap and easy solution?

 

[CBF]

it won't work, the hotwater is re-filled by the small tank on top & with a pump on the hot you will empty that in seconds because it won't be able to re-fill quick enough