Boilers - one for pigletjohn maybe?

[thomasbodley]

We have a typical London terraced 'cottage' with a converted loft. There are two bathrooms, both with baths and wall-mounted showers.

We have a massive Megaflo system that is fairly new, inherited from the previous owner.

However, we constantly run out of hot water in the mornings, even though there are only two of us. It takes 30 minutes or so for the hot water to return, which is infuriating when you're suddenly caught in an ice-cold shower with your hair full of shampoo.

I also loathe not having hot water "on demand" as I did with our old condensing boiler.

Is the remedy to install an even larger Megaflo tank (though Gawd knows where we'd fit it in), or to get a separate condensing boiler that supplies only one bathroom and, say, the kitchen?

I know nothing about plumbing whatsoever, so apologies in advance if this is a really daft question.

Doh, I meant combi, not condensing.

depending on the size of your Megaflow, it should hold at least 100 litres, which is about enough to fill a bath. At full blast you can empty it in ten minutes, maybe less.

A typical modern boiler can reheat a modern cylinder (or Megaflow) in about 20 minutes, so either you have got Drencher showers that waste use vast amounts of water, or there is something wrong.

run each shower into a bucket, see how long it takes to fill, calculate how many litres per minute you are using. Also have a look at the Megaflow and see if it has the capacity written on the side. If not measure it. Have a look at your boiler and see what model it is, and what temperature it is set to.

It is possible to have a combi boiler which also heats the Megaflow. This is not often done, though.

Combis break down more often than system or heat-only boilers as they are more complicated (and some are cheaply made). You would also need to consider how much water per minute comes into the house through the water main. New houses with megaflows usually have an extra-big watermain to get the full benefits.

A powerful boiler also needs a moderately big gas main, all the way from the meter to the boiler.

Thanks so much for this, PigletJohn. So useful. I will definitely get busy with the buckets.

It's interesting what you say about combi boilers not often linked to Megaflows. Why is this? It would mean the best of both worlds, hot water on demand AND decent shower pressure.

BTW, our showers aren't drenchers with the big pan heads, just bog-standard telephone style mains-fed shower mixers.

plumbers gas installers make more profit from quickly bunging in a combi in a day or so, and taking away the old copper cylinder away to sell for scrap. A new boiler complete with separate controls and piping to a cylinder takes longer and they may be lucky to do two in a week. They find it difficult to get customers to pay two or three times as much for that, plus with a combi they have a good chance of repeat business since they might be called back to fit a replacement in 5 to 10 years when the first one is beyond repair.

If your incoming water main only delivers (say) 10 or 12 litres per minute, that is the maximum you can get through all the taps, showers, washing-machine fillers and WC cisterns at any one time, hot and cold added together, so every extra gallon that comes out of the combi is a gallon that doesn't come out of the megaflow. With an old-fashioned cylinder and cold water tank, you have additional stored water so can fill a bath (maybe at 15 litres per minute) at the same time as having a shower, and if pipes have been well-sized, the shower will not lose pressure if someone turns on a tap or flushes a WC, or the dishwasher draws water in. There are also some more high-tech modern methods of achieving this, they are rather expensive.

A typical house may only have a half-inch/15mm incoming water main. If you have two bathrooms, to get the best from a Megaflow or a really big combi, you benefit from a 25mm or even a 32m pipe. It can be quite tiresome digging up the garden and pavement to add a large pipe if the house was built with a small one. British water systems were originally designed and built earlier than in most other parts of the world, with relatively low pressure and flow, hence houses were until recently built with water storage tanks in the loft.

I suggest you also check the temp of your hot water. If you do not have invalids or young children in the house, it can be at 60C and you will have a shower of mixed hot and cold water, so using less volume of hot.

Huge thanks, PigletJohn Got DH to turn up the hot; it's actually quite scary to see how scalding the water gets, but it seems to have done the job.

Managed to shave my legs AND wash and condition my hair this morning in one go, never happens usually [grins]

Long term, I think I will look into that Combi/Megaflo solution, especially when we replace the kitchen and install a downstairs loo.

@ pigletJohn
I have been following your posts , and it seems like you know a lot about boilers and plumbing. We recently bought a house but have hardly any money to renovate it. We wanted to add one more bathroom to the current 4 bd 1 bath we have and have been told by our builders that we need a mega flow .Since we have put in all our funds in buying the house we wanted a minimum quote for megaflow . Which many builders are quoting for more than 8000£ which is ridiculous .could you please kindly advise on a reliable and trustworthy plumber who wouldn't cost us a fortune. Plus it seems like the normal price going around for a megaflow is 2300£.We have also been told to change our old vintage iron cast radiators as the megaflow wouldn't work properly with it. For some reason our pipes are visible outside the walls
Thanks