Water flow not great

[Toastandmarmiteandtea]

We have a mega flo tank (over 20 years old) and have just had three bathrooms renovated. New boiler (not combi). We were hoping new showers would have better water flow but they still arent great and we’d like to improve them. Cold mains water pressure is really good. Something seems to be happening when the hot water is added.
quotes/advice range from new water tank, changing valves, adding a pump, adding an accumulator tank. All are quite expensive and we are happy to pay but really want the best option and not to pay unnecessarily. Any advice? Thank you!

You could try turning the hot water temperature up, then there will be less hot added into the cold and the pressure should be better?

There should be a thermostat on the hot water tank probably behind a plastic panel that says do not remove.

Ah good idea. I need to work out how to do this! Will investigate

Megaflow could well have a fault because they are designed to provide hot water at mains water pressure. They have a few valves and filters around them, and it could be one of these either blocked or broken. It's recommended to get these serviced annually (but I don't. I recharge the gas bubble every now and then when the pressure gets too high). I would not change the thermostat because it should have been calibrated to 60C.
I suggest you try to find someone experienced in servicing megaflows (unvented cylinders/G3 certificate).

I have Megaflo and agree with what JimJamy says.

It may be possible that something is limiting the input pressure in the cold water feed. On my one there is a pressure limiting valve on the cold water feed, a filter on the cold water feed. It is possible that these might be blocked or partially obstructed, especially if you live in a hard water area. Also there is a pressure relief valve on the hot water output that feeds into the tun dish. Also it might be worth checking that the cold water fill tap is fully open.

I had the prv on the hot water side replaced as part of a service. I would probably get someone to come and service. As pp says you need G3 qualified plumber (which can be harder to get).

I think after 20 years it is probably due a service ! For my one if you google the manufacturer name and service you should get to the webpage. On the web page they offer a service which appears reasonably cheap which apparently includes cleaning the inline water strainers...

Thank you. This is probably a good way to start rather than expensive replacement straight away. I’ll have a look at servicing

You need a Megaflow service engineer. I had mine serviced every year.

Thank you for the advice to contact baxi/megaflo. The man was extremely helpful , however as it’s such an old cylinder, they do not service them. He has however given me a local c3 qualified engineer to contact for advice. He did say it would be more sensible to replace the cylinder rather than try and replace parts. Do people think this really could be the cause of our weaker showers?

If all hot water pressure is low then it's the obvious place to start. All hot water taps (sinks/baths etc) would be affected though.

Cold mains water feeds the tank to fill it and provide pressure. Hot water pipes take hot water from tank to taps/showers etc. Restrictions are therefore in the pipes, tank or showers. Seeing as all your showers have a problem, it's less likely to be them. Pipes are more reliable than megaflows.

You say Cold mains water pressure is really good.

But have you measured the flow (litres per minute)?

How old is the house?

Hi piglet John. House is 23 years old. The plumber said the water flow is excellent but I haven’t measured it. It does literally woosh out of the kitchen tap though (cold water). Almost too powerful.

OK, so you have a good supply, I expect there is an obstruction such as a faulty valve, or one that somebody half-shut, for example to hide a noisy pipe.

It does not sound like you will have the inconvenience of needing to renew your supply.

Thank you. So there’s a definite chance that replacing the tank should solve the problem? I will update once we’ve tried that!

Before changing the tank (at great expense) you could unscrew its supply pipe, and squirt it into the bath, to verify the volume and pressure of water being supplied to it.

If it is correct, unscrew the pipe that the water comes out of, and test that.

Only if the supply is good, and the delivery is bad, do you know the fault is in the cylinder.

If you don't do that, you run the risk of replacing a part that is not faulty, and still having the fault.

I don't think anyone can give you any cast iron guarantees that getting a service will resolve the issue. OTHO getting a replacement may be an unnecessary expense.

Megaflos produce greater hot water pressure because the hot water is "driven" by the pressure of the cold water coming in.

If the output pressure of the megaflo (hot water pressure) is low, and the input pressure of the cold water coming in is good, then it stands to reason the problem is somewhere between the input and output. That's all you can really say.

https://megaflo-unvented.co.uk/megaflo-faq/

There is a heading for poor hot water pressure here which touches on some of the stuff that people have already said.

Thank you. I’m not sure even where to start with checking the water inlet to it but good advice. I have someone coming over on Thursday so worth asking these qs

Just a thought but we had a replacement new shower fitted to a mega flo and discovered after fitting that it wasn’t man enough for the megaflo and restricted the water flow. As it’s all 3 new showers it would be worth checking what their water flow is. We had to buy another new one!

Thank you. That would be annoying as the bathroom shop recommended these showers. What would I be looking for? The old showers were rubbish too tho

It was a couple of years ago and my memory is hazy but we ended up with a Mira shower that is amazing.
I checked the flow from the bath taps into a bucket and compared that to the shower. There was a huge difference so we went back to the showroom and they said that the first shower would never work well and sold us a better one.

Also some showers are fitted with flow restrictors check yours aren’t.

Forgot to ask. What is the hot water flow like from the other hot taps, especially the bath tap?

The hot water isn’t great from all the taps. The plumber came this morning. He recharged the megaflo and showed me how to do this for the future. The hot water flow went from 10 litres a minute to 17 so seems much better. Hopefully this will last - he said to keep an eye but a much cheaper option than replacement at this stage. Though likely to need it at some point due to age. Will see how shower feels tomorrow.

update for anyone interested! We ended up replacing the water tank - it was thought it was the inlet valve that needed replacing. As the tank was 23 years old, we decided to replace the whole tank. We now have amazing pressure!

Pinned to the wall of the shower! I love our megaflo!