New shower - which type?

[philhawthorn]

Hi,

I've just moved into a new house and the shower is terrible. It barely has the power to even wet me, if you turn the head upside down water will only trickle out.

It's an electric shower (a Heatrae Sadia 'Dove') which looks quite old. It appears to be fed from the cold water mains pipe. I have a family of four all wanting showers and we can't live with it any more. We have a hot water tank in the airing cupboard and a cold water tank in the loft.

At my old house, we had a combi boiler and a shower (a mixer i think) that fed straight from that, that was fantastic. I was hoping to get something as powerful as that but I'm not sure what type would be best. The cold water pressure is very high, or at least it seems to be when you run the cold tap in the bath, the hot not so great. I'm not sure if a shower coming from both hot and cold water feeds would be good enough to service 4 of us in the morning as the tank isn't that big.

Any thoughts/comments/advice etc. would be greatly appreciated. Thanks in advance.

Phil.

 

[stem]

There are several routes you could follow:

1. Upgrade the existing instantaneous electric shower for a more powerful one. Many older ones are rated at 7kw. Newer ones can be 10kw plus. however, the cable, isolator and circuit protection will almost certainly need replacing to cope with the extra load.

2. If you intend to keep your hot water cylinder a power shower is a great solution. You will need some re-plumbing, as both hot and cold water will need to come directly from the stored supplies via a twin impeller pump which needs to be connected to a 3A fused connection unit. This is not a good solution if you intend to replace your boiler for a combi in the future as the hot water cylinder will then go. You can still upgrade your boiler in the future for a modern efficient (non combi) condensing one and keep the hot water cylinder.

3. If you are going to have a new combi, you could have the solution you had at your old house.

 

[philhawthorn]

Thanks for your reply Stem.

I *think* i'm going to have to go for the electric shower despite the poorer flow as I can't risk running out of water in the morning. I'd love a power shower, but I think our tank would be empty in minutes.

The other option would be a combi like you say, but I don't think the system has been in that long and it seems a shame to chuck it all out just for the sake of a shower.

Thanks again,
Phil.

 

[ColJack]

you have good preasure at the bath taps but not the shower?

check that the isolation valve is not half closed..

or are you saying that to get it warm enough you have to turn the flow down to just a trickle?

 

[bernardgreen]

The other option would be a combi like you say, but I don't think the system has been in that long and it seems a shame to chuck it all out just for the sake of a shower.

Thanks again,
Phil.

Keep the hot water tank and use a pumped power shower or raise the cold water tank higher in the loft. ( Raising it 3 foot will noticably increase the flow rate of an un-pumped shower. )

Only change to a combi as very last resort. They are idea for lazy installers but a pain to live with.

 

[philhawthorn]

Thanks ColJack and bernardgreen for your responses.

Armed with a jug and a stop watch, I observed the following from my bathroom:

1. Cold bath tap delivers ~20 litres of water per minute
2. Mixer tap at sensible temperature delivers ~15 litres of water per minute (hot has less pressure than cold)
3. Shower on coldest setting delivers ~5 litres per minute
4. Shower at sensible temperature delivers <2 litres of water per minute

Soooo, I think the pressure in the system is OK (am i right?) but the shower isn't then able to heat the water quick enough to spit it out at a sensible rate? Question is, if I get the most powerful electric shower (in terms of KW rating) that I can find on the market (a Mira Sport Max at 10.8KW), that will give me 5 litres of water per minute in summer max (Mira told me) would this still be only likely to give me a measly 2 litres in the winter? Are all electric showers inherently this poor?

I do plan to keep the the hot water tank but my other half is reluctant to allow me to run a shower off the tank as she thinks it will use all the water up (for her bath) in the morning (I get up first), the tank is around 120 litre capacity so it would be empty after 8 mins.

Why does everyone seem to hate combis, I thought they were 'the best'?

I'm destined for a rubbish shower aren't I? Give it to me straight, I can take it

 

[JohnD]

A hot water cylinder can heat up from cold in about 20 minutes (this is "best case") so your wife's bath may be safe. If you cut your toenails, brush teeth etc after getting out of the shower, and she does hers before getting into the bath, this may give time for it to refill with hot.

And you might consider getting a bigger cylinder.

 

[philhawthorn]

This is excellent news, i get up way before anyone else in the house to walk the dog...maybe a decent shower isn't out of reach after all. I'm about to drain all the hot water from the tank to see how quickly it will re-heat. All very scientifically of course.

Thanks,
Phil.

 

[JohnD]

Make sure you use it to have a hot bath! Or perhaps bath the dog?

 

[bernardgreen]

I'm about to drain all the hot water from the tank to see how quickly it will re-heat. All very scientifically of course.

If the boiler is on for hot water while you have your shower it will heating water as you shower. So the "recovery" time is quite short.

Yes electric showers are that poor, the only drenching shower I have had from electric was at a friend's house in Germany, 15 kilowatt on three phase supply.

Combi's are a compromise between least install work and what the customer needs. And the customer lost out,

 

[stem]

Remember as well, that a pumped power shower uses a hot and cold water mix so only a percentage of the water used will come from the hot cylinder.

We have a power shower we inherited when we bought the house. Initially the cylinder was heated by gravity and it ran cold after 2 showers. Since converting the system to fully pumped, we've had 4 consecutive showers out of it and the water's still been hot. The water is heated during the time the shower is being used and drying off afterwards before the next user.

Regarding your question about combis, here are my opinions; they are easier to install, so installers love them. For a start they don't need tanks in the loft, or a hot water cylinder and all the pipework that goes with them. The big plus is that they have their controls inside the cabinet and only need a mains supply and single cable running to the room thermostat. Often the installer will connect these without the need to call in an electrician (big saving for the installer). From a DIY point of view there's not much if anything you can fix yourself. A traditional boiler has the pump, programmer, cylinder thermostat and motorised valves outside the casing, perfect for DIY repairs.

Modern combis with a large output can produce a decent flow of hot water but these boilers are then often bigger than needed for the central heating. The gas burner does "modulate" to suit demand, but depending on the size of your installation you can end up with a physically larger and noiser boiler (beause it always fires at full rate when starting from cold) than if you used a traditional boiler that is sized to suit the radiators. They are also quite complicated and have more parts to fail making them more prone to breakdown. (check out the posts on this site) Servicing is also more expensive.

If your combi fails completely you will not have heating or hot water. With a non combi boiler and a cylinder you will (probably) have an immersion heater as a back up for hot water.

Many feel combis are more efficient because you don't waste the heat lost by stored hot water in the cylinder. If the cylinder is well insulated this is not a real problem and in the winter it adds heat the house and airs your clothes as you will have a working airing cupboard.

However with a combi many people find that when they turn on a hot tap to wash their hands, the boiler fires it takes time to heat the boiler from cold and then for the water to reach the taps. Meanwhile you've washed your hands in cold water and turned the tap off, so the gas you've used is wasted. Some boilers overcome this by firing the boiler every so often to keep it warm just in case you want some water using even more gas.

Some feel combis are more efficient than Non-combi boilers. This is not true. Condensing boilers are available in the same efficiencies whether combi or not.

 

[philhawthorn]

Thanks everyone for your helpful responses.

I have decided that we will keep the existing boiler system and run a mixer shower from the tank, I've done my scientific experiments and the water will re-heat in time.

I may go for a pumped solution, but one more thing, I don't understand how (stem) you can get more showers from a pumped rather than just a gravity fed system, surely the pumped system uses more water and therefore more hot?

 

[JohnD]

"cylinder was heated by gravity" means that the heat from the boiler reached the cylinder only by thermosyphoning. More modern (since 1960's ) practice is to pump the circulating (primary) hot water from the boiler. This makes it travel faster and so the cylinder gets hot faster.

It seems quite common for solid-fuel boilers multifuel stoves and backboilers to rely on gravity circulation. These systems can be very simple and may have no electric controls or mechanisms.

 

[stem]

I don't understand how (stem) you can get more showers from a pumped rather than just a gravity fed system, surely the pumped system uses more water and therefore more hot?

The pump I was refering to is one pumping hot water from the boiler to the hot water cylinder, not the shower pump. JD's post above explains. Sorry for any confusion.