Guidance on upgrading shower / flow rate

[howartp]

Hi,

We're in the process of getting a new bathroom, and I'd like to do something with the shower while we're at it.

I used to grumble about it being 'slow' but I just thought that was me being me - noone else in the family complained. That was until we went on holiday this year, and the Aqualisa Mixer Shower in my ensuite was absolutely brilliant - I never knew such a powerful shower existed.

Our current setup is:

7.5 Kw Electric shower, fed off cold mains feed, 6mm cable with 35A fuse. (Through isolating pull switch)

The rest of the bathroom, plus the kitchen, is also fed off cold mains (so the shower gets hot when you use the kitchen or bathroom taps!)

We have a 117 Litre hot cylinder on same level as bath, fed from the cold tank.

We have a ~21 gallon cold tank in loft, with approx 0.5m head between base of tank and showerhead.

Flow rate through shower is 4.3 litres per minute (which appears to be above average for an electric shower, but it is still too slow for my liking )

Stopcock is (almost) fully open.

I worked out that 35A * 240v = 8400 so IF we just got a larger electric shower, we'd obviously need a larger fuse and presumably (to make any major difference) we'd need to upgrade to 10mm cable? I don't just want a 8.5Kw. This obviously involves a bit of work.

Therefore I was wondering what else we could do - if we're going to have to do some work to get a result, then it is worth looking at what alternatives there are, even if they also require work. I would personally like a Mixer Shower if possible. I read a post somewhere yesterday which mentioned putting a pressure device in then using a Mixer Shower for a similar setup to mine?

Any advice/suggestions would be greatfully received.

If I've said something wrong, please let me know!

Cheers,

Peter

 

[ChrisR]

Your shower flow will drop to about 3 l/min in the wiinter, and a 10kW would only be about 4.

If you plumb the shower cold to be from the loft tank, and you use a mixer for low pressure, you would get slightly more water but not a lot, so you need a pump. Then you need a bigger loft tank, like 50 litres, or you could empty it.

You could bring the cold (& hot) straight down from the loft instead of replumbing the bathroom - see Aqualisa Quartz, pumped type.

 

[howartp]

Hi Chris,

I'm not following what your saying/suggesting.

I understand the first paragraph about the flow dropping in winter, and hence a 10Kw in winter would provide less flow than we get now in Summer. So staying electric is no good.

I understand the 2nd paragraph - if I bring the cold from the cold tank, then both hot and cold will be same pressure so I can use a normal mixer, but I'd need a pump to increase flow, and hence need a larger cold tank.

Not sure about the 3rd paragraph - Are the 2nd and 3rd paragraphs the same thing? How could I bring the hot down from the loft, when the hot is coming from the cylinder on same floor ('upstairs') as the bathroom. (We're in a standard upstairs/downstairs house with loft). Not sure how bringing either of the hot/cold down from the loft prevents replumbing the bathroom; something will need replumbing to do this? (We're replacing the entire bath, sink, loo, flooring, wall tiles and putting in a false ceiling so replumbing and/or wiring isn't a problem within the bathroom (and loft))

Which Quartz were you thinking of - I like the look (but not price ) of the Digital version, with the seperate processor. But presumably with this either the hot would need pumping or the cold would need slowing.

Please explain further what you were thinking.

I have the Aqualisa general brochure AND the Aqualisa Quartz brochure because I ordered the general one when we came back off holiday last year, and the Quartz came with it.

Thanks,

Peter

 

[howartp]

Chris?

Any chance of a reply?

Thanks,

Peter

 

[ChrisR]

Basic problem is that you wouldn't choose to try to mix mains cold and tank hot in a mixer because the pressures are unbalanced. You don't pump the mains.

So cold has to come from loft tank, as well as hot (via cylinder).

Quarttz can make pkllumbing a bit easier.

Option can be a Venturi shower (google), which DOES use mains cold and tank hot. They're ok but not a thrill.

 

[howartp]

Ah right.

That explains my misunderstanding.

I've already looked at the Venturi showers but I'm not particularly enthused by them.

If I brought another cold down into the airing cupboard (which is directly underneath the cold tank) and put the quartz pump in there, the easiest route back with the pumped output would be back up into the loft, across the edge of the loft, then back down into bathroom. The quartz is rated at 18 litres a minute max - how much is this likely to reduce if I pumped it upwards as above. Will it still be significantly more powerful than the 4 litres a minute we get currently? (Loft floor is approx 1.5 metres above top of hot cylinder)

Thanks for quick response,

Peter