My incoming water main

[Bod ...]

Megaflow used to stipulat that their units need a 22mm incoming main. Then they realised that this was loosing them business as this isn't always practical.

I've fitted plenty of unvented cylinders with 15mm feeds and they work fine. If the customer is not happy with pressure then that's a different matter.

If you have a big house with many bathrooms then yes he has a point.
Then a break tank and pump might be considered.

I can only think of one part of my town that I would question fitting an unvented or even a combi. The pressure is too low regardless of a 22mm or 15mm mains feed.

 

[dormermike]

Megaflow used to stipulat that their units need a 22mm incoming main. Then they realised that this was loosing them business as this isn't always practical.

I've fitted plenty of unvented cylinders with 15mm feeds and they work fine. If the customer is not happy with pressure then that's a different matter.

If you have a big house with many bathrooms then yes he has a point.
Then a break tank and pump might be considered.

I can only think of one part of my town that I would question fitting an unvented or even a combi. The pressure is too low regardless of a 22mm or 15mm mains feed.

What's the flow rate in that part of your town out of interest?

Have you fitted lots of unvented to 15lpm supplies and customers happy?

It's a big expense (7k) for me anyway and I really need the space that's currently taken up by the tanks etc, to move that stuff downstairs. I'm just trying to guage realistically what I should expect once it's in to avoid disappointment.

Would a combi make better use of the incoming flow rate?

Other option is upgrade the incomer and I'm looking into that too, doesn't look too expensive, cheaper than an accumulator (£1500 fitted).

 

[Bod ...]

What's the flow rate in that part of your town out of interest?

Have you fitted lots of unvented to 15lpm supplies and customers happy?

It's a big expense (7k) for me anyway and I really need the space that's currently taken up by the tanks etc, to move that stuff downstairs. I'm just trying to guage realistically what I should expect once it's in to avoid disappointment.

Would a combi make better use of the incoming flow rate?

Other option is upgrade the incomer and I'm looking into that too, doesn't look too expensive, cheaper than an accumulator (£1500 fitted).

A combi is not the answer.

I'm not sure about flow rates in that part of town but this is all what a plumber can measure for you.
The high the better. And if you get 3 bar your ¾ of the way there.

 

[Madrab]

The size of pipe isn't important when it comes to designing an unvented installation, dynamic flow and pressure is. If there is adequate pressure then a 15mm pipe can flow more than enough to satisfy an unvented, the only issue with that will be excessive water noise and wear as the water velocity in a 15mm pipe will be significantly higher than an equivalent flow through a 22mm pipe.

So I'm only getting 15Lpm at the moment. If I replace that 15mm with a 21 to 22mm pipe will I get more flow?

Not necessarily, it all comes down to the mains' dynamic readings.

You haven't said what your property is like, how many bathrooms, showers, baths outlets and how you want to use it, lots of open hot taps/showers/baths at the same time etc.

 

[dormermike]

You haven't said what your property is like, how many bathrooms, showers, baths outlets and how you want to use it, lots of open hot taps/showers/baths at the same time etc.

It's an approx 200sqm bungalow, 5 bedroom, converted so there is an upstairs, has 3 bathrooms, 3 showers, 1 bath. The bath and one of the showers is ground floor right next to where the boiler currently is, which is where I'd like the new tank to go ideally.

12 rads, 35sqm of underfloor going in later this year.

Occupancy is four, with 3 here all the time, so 2 showers on at a time is a possibility.

 

[Madrab]

OK, given those requirements and limitations then ideally stored, unvented HW would be the ideal.

First thing that needs to happen is you want to make a call to your water transporter. Just say you're having intermittent problems with your mains fluctuating and can you have someone out to do some tests. Try and be there when they call so you can have tea and biccies ready to go and get them on board so you can get as many test performed as possible.

You want to find out how well the mains can perform and want definitive dynamic mains pressure and flow figures, that will give a starting point as to what approach may be able to be taken.