Can this electrically heated shower system be made to work?

[sammydavis]

I've only had gas combi fed showers for the last 20 years so I've lost a sense of electrically heated water systems and how they work.

Went to see a top floor (3rd floor) 1960s flat yesterday. Water is electrically heated and heating is via storage heaters - no gas in building.

The building is flat roofed.

In the bathroom there is a shower fed through bath mixer taps (the type you pull a lever to swich from bath taps to shower head).

In the cupboard next to the bathroom is the copper tank/immersion heater and above the copper tank (at my head height) was another square metal water tank - about 18" wide and high - I've assumed this is a cold water tank feeding the copper tank - would the water from this also feed the kitchen cold taps?

I tried the cold water tap in the kitchen and having tested my own cold water flow at much more than 15 litres per min - I would have estimated the flow on this cold water tap to be less than 10 litres - substantially less - maybe 6-8 litres per min.

Unfortunately, I didn't get to try the shower water flow/pressure.

But... can an system with an immerion tank lower than the shower head and a cold water tank level with the shower head, with low mains pressure/flow - can that really offer a decent shower?

Is there a solution? - bearing in mind there is no space to put a tank higher up - would a mains fed electric shower over the bath work better (is that feasible?) is there a pump that would help? - or is the water flow too low for that?

The cold tap at the kitchen sink will (should) be fed from the incoming main. If the kitchen tap is a flashy ceramic mixer it will restrict the flow and a Bristan pillar tap will give better flow.

The bath shower will depend on height of the cold water tank above the outlet.

It is technically possible to fit a shower pump to suck the water from the tank (not the main) and squirt it at you, but they are rather noisy, and in an old flat, your neighbours would get annoyed and kill you.

P.s.
If it is 1960's top floor, flat roof, it will be badly insulated.

Thanks PigletJohn - the kitchen tap wasn't a mixer, probably an 80's fitting with separate hot and cold. It looked quite limescaley but not bad enough to restrict the waterflow too much.

So, if, when you stand in the bath, the shower head is raised above my head and consequently, above the level of the cold water tank - will there only be a trickle of hot water?

Would installing an electric shower off the mains cold supply be an improvement on the existing bath mixer tap or would it basically be a lower flow of the kitchen cold tap? Does a 'restrictive'/smaller holes shower head give the impression of greater pressure?

Also, on a separate but related point, I've been googling to try and find out how long it takes to reheat a whole copper tank of water for two consecutive baths. For a modern coppertank/immersion I've seen estimates of 2 1/2 hours - does that sound realistic for a minimum 20 year old immersion with a standard size copper tank.

Thanks for the tip on the insulation in the roof - just gets better

Would I benefit from the poor insulation in the floors below me though?

if the shower head is raised abover the top of the cold tank water level, nothing will come out of it.

If the cylinder is bare copper, it is very badly insulated and will waste lots of heat. Luckily you can easily fix this by putting a couple of red jackets on it. The previous occupier might have left it bare so the wasted heat warmed the icy bathroom. If the flat has economy 7 electricity it could be fitted with a modern, bigger, better insulated cylinder with two immersion heaters, the cheap-rate one at the bottom. An immersion heater at the top does not usually provide enough hot water for a deep bath. The previous occupier might have been quite old and not used to good heating and plumbing.

if the cold water flow and pressure are poor, an electric shower will have poor flow and presure. Electric showers have pathetic flow anyway, especially in winter. If this building is not up to modern standars the incoming electric main and company fuse may be too small to supply an electric shower.

the amount of heat that falls through your ceiling will be much greater than the amount that rises through the floor.

If the building is ever given a new roof, I expect it will be brought up to sensible levels of insulation.

I hope this flat is very cheap

I hope this flat is very cheap

Ha ha - don't!

You're making it sound like a nightmare!

I think the flat roof was recovered about 20 years ago (so that's probably due again soon too!)

It's a bog standard 1970s block but the location is right and the price fits my budget - it's got recent double glazing and the block has been maintained but yes, it's built to 40 year old standards.

I think the immersion tank has red jackets on it at the moment and the immersion and cold water tank are in a cupboard nex door. The bathroom is internal (centre of building) so no window - not icy just damp - seriously not too damp, it has an extractor fitted.

It runs on economy 7 at the moment so it must have 2 immersions - which is good. But any replacement apparatus would have to go in the same location - so couldn't be any bigger.

Could a pump or suction apparatus be attached to the incoming main (inside the flat) to increase the flow of water? Does that kind of thing exist?

you are not allowed to suck water out of the main.

Ah well, so given that I can't magic up a 21st century uber house, in the right location, at the right price, I just have to work with what there is - c'est la vie.

As long as the water company are supplying at their standard pressure, I can only make any possible adjustments/adaptations with what they supply and within the limitations of the flat and existing technology.

Still, I'm not the first person to have this problem and I won't be the last - Down to the plumbers' merchants on Monday to see what they can suggest - thanks for all the advice.

the cold water flow sounds quite disappointing. Modern flats have an individual supply pipe run to the mains in the street, but yours might have a shared rising main, probably of smaller size than is usual today. It probably comes up a plumbing duct in the kitchen or airing cupboard. In flats, it is fairly impractical to improve this unless the whole block is being replumbed. If there was a better supply you could have a white pressurised cylinder.

You can find the stopcock, probably in the airing cupboard or under the kitchen sink, and verify that it is full on, but anything less than 12 litres per minute is going to give a disappointing shower; and if it is a shared main, will drop when your downstairs neighbours run their taps (hence the cold water tanks each flat has to buffer usage)

Cheers PigletJohn - yes - I found the main stop cock at ceiling height by the entrance to the flat. It probably does come in via a central duct/shaft. Unfortunately, I didn't test if it was fully open.

That would mean though, that the mains was above head height in the bathroom - if that makes any difference to say, a plumbed in electric shower?

I guess it just means the shower is supplied with cold at the maximum of the measley pressure?

The flow certainly visually appeared to be less than 12 litres per min.

I've been looking at electric showers which seem to operate on a minimum water input pressure of 0.9 bar but I don't really understand the relationship between flow and pressure?

How would say 8 litres per minute translate in 'pressure bars'?

there is no relationship between pressure and flow.

e.g. the top of Niagra Falls might have zero pressure but a cubic mile a minute of flow. A dentists injection syringe might have 1 bar of pressure in the needle and deliver 5ml per minute.

1 bar of pressure is provided by 10 metres height tank to tap.

It doesn't matter whether the pipe enters from the top or the bottom, though entering from the top might make me suspect there was a water tank on the roof.

No tank on the roof - I can see it on Google satellite.

I kind of get what your saying about flow and pressure - but not really

I understand that 'pressure' could be like punching somebody once every 15mins really hard = high pressure but low flow

Where high flow could be 1 punch per minute of variable power/force.

But with water.... if I was getting 20 litres per minute surely this would require some 'minimum' level of pressure? A higher level than would produce 5 litres per minute?

There must be some relationship as without pressure there would be no flow - surely? and vice versa.

Also there must be a way of creating pressure other than via height otherwise bungalows would be stuffed - although I get the analogy. But if you drop a litre of water from 10 metres does it create the same pressure/impact as dropping a 1000 litres from 10 metres?

I mention the pressure requirement on the showers because that's the manufacturer's specification - they don't mention a flow requirement but obviously it won't work below a certain flow.

There must be an equivalence between the two measures for technical expression - i.e. when the manufacturer says it requires a minimum of 0.9 bar they must have in mind a minimum flow that will create that pressure?

I'm no physicist so I may be wrong

ok then "for plumbing inside a bathroom, there is almost no relationship between pressure and flow." (it does make a difference at the water main)

the 1 bar/10 metres is the pressure. It doesn't matter if there is a thousand litres or one litre of water in the tank at the top.

However, if there is a very narrow pipe, you will not get as much flow out of it as is there was a very wide pipe. If you put a small tap on a big pipe, the pressure will hardly change. If you put a big tap on a small pipe, the pressure where it comes out of the tap will drop.

Bungalows always have low pressure if they are relying on a tank. If however thee taps are fed from the mains for cold, and a combi or megaflo for hot, they will have high static pressure. However if they have small internal pipes, or a small supply pipe to the road, they will have poor flow.

May older houses have a 15mm or half-inch supply pipe, and get poor flow. This is very noticable if they have more than one bathroom or shower, and the flow has to be shared between several users after a storage tank has been removed to fit a combi. If this narrow pipe is replaced with a 25mm or 32mm plastic pipe, they will have much better flow. This is necessary to get the best out of a megaflo, and advisable for a larger combi.

...my bath taps are supplied in 22mm pipe from a large loft tank about three metres above. The (separate) hot and cold taps can each, at the same time, deliver 15 litres per minute at a fairly low pressure of about 0.3bar. The big delivery is due to the short, wide pipes and the non-constrictive taps. A mixertap, especially a ceramic disc one, would constrict the flow.

However the incoming water main only delivers about 12 lpm. It is however at higher pressure. No matter what size pipes and taps I fitted to the main, I would never get more than 12 lpm out of them, even if I had twenty taps. This is a problem many people are surprised by when they get a combi and it takes ten minutes to fill a bath, instead of four.

The shower manufacturers will mean the pressure that goes to the shower when it is running. So to get a reasonable shower you need (say) 10 lpm minimum, at (say) 1bar

In the flat you are looking at, from the information you have given, you won't get that. You might perhaps get 6 litres per minute if it comes straight off the main, which will be a very weedy shower

oops, just checked (I measured it for an earlier thread)

my hot bath tap will fill a 2-gallon bucket from the hot tap in 27 seconds. That's 9 liters in 27 secs, so (( 9/27) x 60) it delivers 20 litres per min

The cold tap will do the same, at the same time. My baths fill quickly.

I love my tank

Cheers PigletJohn - it's complicated!

So, in a way, you're creating your own internal 'water system' where (by the use of storage tanks and height) you can vary the pressure compared to the mains supply.

And this is the option I won't have!

The bit that particularly confuses me though is.... if the current flow in the flat is 6-8 lpm and assuming with the shower above my head there would be no water output.
At this point I have no measurement of water pressure.

Although, would I be right in thinking that if the mains pressure was high it would force the 6-8 litres up and out the shower head (but not the hot water as that relies on the tank above the immersion).

So, by using an electric shower run off the cold main, would I bypass the flat's internal 'water system' and bypass the zilch height pressure from the immersion tank and should get marginally more pressure than relying on the force of 30 gallons at head height?

For arguments sake.... if I went back to the flat and found (I wish) that the stopcock was in fact half closed - if I open it and let's say increased the flow to 15 lpm, this would surely give me a more effective electric shower (ignoring the immersion tank)? even if it would not affect the flow or pressure of water from the immersion tank?

Does that make sense?

I think this is probably just confusing me ....without resolving a very preactical problem because what I want is increased flow .... more water in the shower.... and you're saying it has no connection to pressure but if I was able to put a tank on the roof of the flats that would improve pressure and flow - so it is connected...?

If I get more water though the pipe an electric shower will work better.

If I could increase the pressure by putting a tank on the roof the pressure from the immersion would be higher and my shower would be better.

In that case the lack of pressure is entirely controlling the flow.

Unlike in your house (where you manufacture higher pressure) I can't manufacture pressure (because I haven't got height) so I can't increase / or create flow at the shower head.

I don't understand how they can not be connected?

the flow is mostly dependent on the diameter of the pipes from the source. The source might be a tank, or it might be the water main in the street. In your case it is poor so I am presuming a half-inch pipe. Apart from making sure the stopcock is fully open, there is nothing you can do to improve it, because I think it will be impractical for you to lay a new larger pipe through the rest of the block and under the pavement.

The length of the pipe also affects the flow, but inside a flat is not as significant as the pipe diameter.

You could get better flow to the bath taps by increasing the size of the pipes from the tank to the tap. For example, if you cut a six-inch hole in the tank, the water would gush out faster than if you made a half-inch hole in it. The pressure would not change. Thus, you could fill up the bath faster, but at low pressure, with 22mm pipes than with 15mm pipes. This is fine for a bath. It probably already has 22mm pipes.

You will not have adequate pressure from the tank for a shower. The bathtap attachment will only be useful for washing your hair kneeling in the bath.

You could fit an electric shower to the incoming water main; it would normally give you less flow than the kitchen tap because the shower, and the jets in the head, constrict the flow. In your case the kitchen cold tap flow is already poor. The pressure might be adequate. Put your thumb on the spout of the kitchen cold tap and see if it will squirt the ceiling.

It is possible to fit a pump on the tanked water supply to squirt the hot and cold shower (you are not allowed to put a pump on the watermain supply). Shower pumps are quite noisy and will anger your neighbours.

Thanks PigletJohn - I think the conclusion is there's no perfect solution.

Without the ability to fill a water tank at a great height, I have no real means of altering the flat's internal water pressure.

As in your house, if your mains water is delivered at 12 lpm and you fill a tank which you proceed to empty at 15 or 20 lpm then eventually your flow will drop because your tank is being drained faster than it is filling - tank capacity is the key for you.

I guess the key for me would be knowing whether the diameter of the pipes inside the flat in any way restricts the flow from that available at the source pre-stopcock.

If that was the case though, i.e., if the pipes were narrower, I would expect the 'illusion' of greater pressure.

Isn't this what happens in a shower? If you attach a pinholed shower head to a water supply, neither the pressure or flow are changed.... but the illusion/effect is of greater pressure ...created by forcing the same amount of water through a number of smaller openings.

If you have a half inch water outlet, which gives a gentle flow of water and you then attach a shower hear restricting the opening to 20 miniscule holes, - it will 'feel' as though the water is coming at higher pressure ... when in fact the effect is created because the flow is reduced/restricted?

That's what I want to achieve. To harness the limited power of the existing flow and pressure into the form of a shower which 'appears' to have reasonable force.

So widening pipes inside the flat, unless there's already a measurable restriction on the flow compareed to the outside... might not help.

But a restrictive shower head, using the exisiting flow, might give a 'sense/feeling/illusion/' of an effective shower..... as long as the restricted flow can reach head height.