Choosing Shower and checking water pressure

[kevin_robson]

I am about to fit an electric shower. There are two parts to this question.

I'm after the best flow I can get so am going to go for a 10.8KW electric shower. In the past I've had a Mira Sport 10.8 which was pretty good but I note it is very expensive compared to other 10.8s. The other one that seems to crop up and is a lot cheaper is a Triton.
Is the Mira much better to justify the price difference or does it not really matter if they are the same power rating? What are Tritons like?

The second part concerns the water flow. How can I check the water flow is sufficent. The instructions say 11 litres per minute is required which I can easily check, but also mentions about 1-10 bar being required. How do I check that?

Also, is the anti-limescale feature advertised on Triton showers really work - I note that the warranty for limescale is only 2 years anyway!!

Finally, are the digital guages any good or are they just fiddly.

All advice gratefully appreciated.

Thanks

 

[chainsaw_masochist]

You can obtain a pressure tester from your plumbers merchants - they range from about £12 - £40. It is probably easiest to attach this to an outside bib-tap if you have one. Otherwise you will need to connect it to your kitchen tap (cold supply) and this might mean that you need to buy a few items in order to make it compatible.

The difference between Mira and Triton showers is pretty much down to quality. I have fitted one of each of these previously. The Mira (9.5kw) cost about £250 and the Triton (10.5kw) £110, the latter having been bought at half price from a shed. The Mira was the larger unit of the two, with a noticeably sturdier casing. The electric terminals in the Mira were also more substantial; the Triton equivalents looking to be a bit weedy, odd really, seeing as they would be dealing with higher currents.

That said, the Triton did have a few extra lights to denote things like low pressure, economy setting etc and would seem to offer good value. Do a search and see whether there are other views on these items.

I am assuming that you have a 50amp MCB, an RCB and 10mm cable already installed for this work?

 

[ChrisR]

See if you can hold the mains back with your thumb on a garden tap hose spigot. If not, you have plenty of pressure. A strong thumb can hold about 3 bar.

I keep hearing that electric showers only just last longer than their guarantee period. I'd go for the cheapest, by price divided by gtee years!

Their flows depend ONLY on the kW rating - they're all poor.

 

[kevin_robson]

Thanks for replies. I will try keeping my thumb over the tab and see if I can hold the water. I measured the flow rate last night and it took around 40-45 seconds to fill 12 litres into a bucket. I believe the required amount is about 11 litres per minute so that should be OK.

However, I'm assuming this is different to actual water pressure. One thing I noticed was that the pipes for the existing (non-electric) shower both come down from the loft so I am wondering whether the cold water for the house will come from a tank in the loft rather than from the ground from the mains. Does this sound right for a 1950s house in the UK? If it is the case that the cold water is supplied from a tank in the loft can this still be used for a 10.8KW electric shower?

Sorry to go on, its just I want to make sure its going to work before I shell out money on it.

P.S. Just moved in to the house so have an electrician re-wiring it, so will get all the necessery electrics put in by him.

 

[chainsaw_masochist]

The cold that comes down from your loft is likely to be supplied from the tank. Check this by turning off the gate valve that supplies the cold distribution pipe from your cw cistern – the cold supply to the shower should stop running. If this is not the case then turn off the stopcock that supplies the house just to ensure that it is mains supplied. It is unlikely because unless a pressure reducing valve was incorporated in the supply pipe there would very likely be balancing problems when using the existing shower.

Now if you want to fit what is called an electric instantaneous shower you are not going to be able to use a tank supply. You will need to run a separate supply teed off from your existing mains pipe (with a double-check valve to prevent siphonage) to the shower. Sounds like quite a bit of work.

If you have established that your cold is tank supplied, then what you can use is an electric pumped shower. These look pretty similar to the electric instantaneous showers but have an integral pump. They require only the cold as inpput. I have not fitted such an item but am aware that Triton have a model called a T80si.

What would seem to offer the best solution, seeing as you have both hot and cold supplies, is to have a mixer shower fitted in your bathroom with a separate pump to boost the pressure. Would this be a problem? Admittedly they are pricier.

 

[kevin_robson]

Thanks. I have spoken to Mira this morning and they have pretty much told me the same thing re the built in booster models they do.
I will go to the house tonight and work out for definite where the water is coming from.
If (as I assume) the cold water is coming from the tank then one of thee boosted models would seem to be the best solution.

I have thought about just putting a mixer on, but I like the idea of not having to worry about running out of hot water with the electric shower. I will give it some thought though, as presumably the water flow would be better from a mixer shower than an electric one wouldn't it? providing we had enough hot water capability.

Decisions Decisions!
Thanks again for your help

 

[chainsaw_masochist]

I will give it some thought though, as presumably the water flow would be better from a mixer shower than an electric one wouldn't it?

Depends on prevailing head of water ie how high the cistern is above the shower. If it is only 1 metre or so then to get a decent flow it would be necessary to add a booster pump. This type of pump can be hidden under the bath. What is the flow like on the exisiting shower?

 

[kevin_robson]

The existing mixer shower is pretty crap flow - coming off the tank.
Will defintly have to either find the water main on the way up to the loft and get a normal electric shower, or get the pumped shower and take it off the tank. Tank is only 25 gallons though and I was told I would need 33 gallons - it just gets more compilcated by the day.

 

[chainsaw_masochist]

The existing mixer shower is pretty rubbish flow - coming off the tank.
Will defintly have to either find the water main on the way up to the loft and get a normal electric shower, or get the pumped shower and take it off the tank. Tank is only 25 gallons though and I was told I would need 33 gallons - it just gets more compilcated by the day.

Well in that case you probably are better off going for the electric instantaneous after all. Keep us posted.

 

[kevin_robson]

OK. We have fitted the standard Mira sport. Took the feed off the mains supply on its way to the tank and the pressure/flow seems pretty high through the pipe.

Have not tried the shower itself as the electrician has not finished his bit but hopefully it should all work fine when powered up.

Thanks once again for the advice - will post once more hopefully with good news re its performance.

 

[kevin_robson]

Good news. The shower seems to be working fine.
The only downside is the flow rate doesn't seem any greater (and possible a bit less) than the 8.5KW shower fitted in my current rental property.

I don't think it is a case of not enough flow as to get it hot I need it on the HIGH setting with the control over half way, just like on the 8.5KW one.

As I said it works, I just dont see where the extra money went on the 10.8KW Mira Sport.

Any ideas why this could be?

 

[chainsaw_masochist]

Sorry about the delay Kev, but I have been away on holiday.

As I said previously I fitted a 10.5kw shower which produces a pretty good output flow from the head. This was from a supply of 2.4 bar and a flow of 14 litres per min flow. I would measure the pressure as described previously and if you have less than 1 bar (though this is not very high and may not provide great performance from your new shower) then take it up with your local supplier.