hot water output to 5 bath property

[cjjemam]

Hi all,
Please be gentle as this is my first time. I am looking for advice on the best type of hot water supply to shower outlets in my property. I'm currently renovating and extending it and will eventually end up with 4 ensuite bathrooms and 1 house bathroom.

Three of the ensuites will all have mains fed thermostatic mixer valves, the house bathroom will have a bath and shower with therm mixer, and the last ensuite will have a bath and therm mixer with six body jets.

I originally toyed with the idea of using a system boiler with a couple of cylinders in the loft and sharing the stored hot water amongst the showers using a pump for each shower, and keeping the existing combi (ravenheat) to feed all other hot water outlets. However, my local plumbers merchants have said that the Vaillant unistor should be able to cope. Is this true? I believe that the unistor is only as good as the mains pressure, which in my case delivers 14litres per min at the kitchen tap (its fed via 1/2 inch lead which I'm probably going to change to 25mm mdpe). Is there a combi that could handle it?

There are 6 of us in the house, and the four kids are growing up so there's a possibility that sometimes all showers will be in use at once (previous house owner had a damn water meter fitted - boo).

Basically I want it to be done right so it doesn't have to be altered in future and I'm hearing conflicting advice. Things you need to know are - space is not an issue, boiler(s) will be in garage, hw storage (if reqd) will be in loft. Cost is an issue, but not overly - I'd sooner have all the showers running right. Finally, the heating requirement is approx. 105000 btus to 18 rads.

Thanks in anticipation, Carl.

 

[Balenza]

cjjemam wrote

14litres per min at the kitchen tap

Forget about it m8. You'd need at least 30L/min for what you propose.

 

[Agile]

I doubt that you realise what your hot water demands really involve.

To have 10 li/min showers for just 10 minutes you need to store 600 litres!

In practice TWO 310 li cylinders will provide this but this will need to be supplied from a 500 litre cistern. Thats quite a size AND weight!

A 32 kW boiler will heat the house and water as they are not both required together.

Even your 24 kW Ravenheat will be adequate as long as its not freezing outside.

Total cost about £6k to £12k for a whole new system!

Tony

 

[giblets]

And you will, of course, be informing your local water supply company ( as required by Water Regs) so that they can install a water meter for you, won't you?

 

[cjjemam]

What I mainly wanted to know was would the largest Vaillant unistor (310l) be able to cope with my showering requirements? I'll be renewing the mains supply pipe so in theory should have greater pressure. Also, I can run one shower off the exisitng combi as well as the other hw outlets. I did say that I'd like to be able to run all showers simultaneously but in reality this would be an extreme rarity, most likely would be 2 running at once, sometimes 3. Finally, I already have a water meter fitted (unfortunately).

Ta, Carl.

 

[Balenza]

cjemam wrote

I'll be renewing the mains supply pipe

Their is no gurantee that this will increase the flowrate to the level you want.
Someone tried it recently on this forum and the flowrate was only marginally better from what I remember.

so in theory should have greater pressure.

It won't raise your pressure. That stays the same.

 

[doitall]

If your serious about this then the answer is to fit 2 300ltr cylinders, a system boiler and a large sectional storage tank and pump set all in the garage or better still cellar if you have one.

 

[cjjemam]

doitall,
This is a possibility as I can create a "boiler room" in the new extension. Do you mean use a whole house pump or pumps to the individual showers? Also, no-one seems to give any replies on the Vaillant unistor. Is this a no-no?

Ta, carl.

 

[JohnD]

I stayed at a place in Australia which had a smallish cylinder for each bathroom (and showers only, no baths)

it mean no-one could hog all the hot water so you didn't need one vast supply to accommodate a shower-hog.

 

[simond]

I think you want a DualStream. It is an accumulator and unvented cylinder package that boosts the flow rate to allow multiple showers as you describe.

If you are keen on the uniSTOR, an experienced plumber could add an accumulator, or you could buy a packaged OSO or Ariston cylinder based DualStream unit.

The uniSTOR would only offer an advantage over the other brands if you were intending to buy a Vaillant boiler AND have only one heating zone. Then you could use their VRT360 or VRC400 control system.

As always, find a tradesman who has experience with this technology if you do not want to be part of his learning curve.

 

[cjjemam]

I am not specifically after the Vaillant, just after something that is up to the job. It's just that my plumbers merchants said the unistor would cope hands down. Perhaps he's on better profits on Vaillant gear!?

 

[simond]

Mercahnts do not fit stuff, they just sell it. Most of us wouldn't buy a car just because the salesman says it is just right for us.

A Vaillant uniSTOR is a good quality product at a not unreasonable price, so I am sure your merchant had the best intentions. Generally the best margins are made on the minority manuacturers who are buying market share, rather than Vaillant who already have it.

If you are in the market for an UV cylinder the merchant made a good proposition. If you need someone to advise you whether a product is suitable for your property, you need a plumbing/heating specialist. As you say, it is only theory that your new water pipe will cut the mustard.

 

[cjjemam]

Thanks, Simon,

I've been on a couple of websites re uv cylinders and accumulators. As I have the space I think this is my best bet although my installer reckons 3 smaller cylinders heated via a small system boiler and pumps to the showers is still a viable and cheaper option. What do you reckon the maintenance costs and the reliability of either system would be? Basically, what are the pros and cons, and is it worthwhile keeping the existing 24kw combi to feed one shower and serve the central heating?

Thanks in anticipation,

Carl.

 

[simond]

I would go for the Dualstream option, they are more reliable and give a better performance than a cluster of domestic pumps.

For more info we have a page on our web site (see my profile) or visit the manufacturer www.gah.co.uk

 

[simond]

Sorry, to answer your last question there is no reason why you should not keep the combi for now and run the HW off the DualStream (via a zone valve), and use the combi HW just for the kitchen sink tap etc.

You could always ditch the combi later when the time is right.