Megaflow or Unvented

[Stunt Sheep]

Hi There Folks

I am looking to replace my current unvented system with a Megaflow type system however one of the plumbers that came to look at the job has told me that we don't have enough pressure to run more that one shower with a Megaflow which is something that's important to us with 3 growing children. The long term plan is to install a 3rd shower so I want to make sure I pick a system that's going to cope. I would ideally like to get rid of the loft tanks if possible as last year they froze and caused problems despite being well insulated. They are also difficult to access due to the small size of the loft space. Would an accumulator solve the pressure problem and if so what size would you suggest for a 300ltr indirect? Also are there recommended brands or ones to avoid? Thank you for your help

 

[Dan Robinson]

A Megaflow is an unvented system. You have an open vented system.

 

[Dan Robinson]

An accumulator won't solve PRESSURE problems without a loading pump. I advise avoiding Megaflow. Overpriced and the internal baffle is not the solution they think it is. We use Joule cylinders and Great Water Accumulators. They do a loading pump.

 

[Stunt Sheep]

Thanks for your helpful reply. I have had mixed information for the plumbers that have priced the job so its useful to get another view point. One told me I could not run more than one shower, one told me it will be fine with just the megaflow and the last one told me its possible but I would need a pump set up or I would be disappointed in its performance.

If I got an accumulator and pump set would that be sufficient for running 2 showers at the same time. Water flow is approx 14ltrs a min, not sure about pressure.

 

[Dan Robinson]

First off you need to know what the mains pressure is.

Accumulators work well but are subject to the downstream pipework. Their main purpose is to eliminate the restrictions upstream:

Regard one we did a few years ago:

Without:

With:

This was without a pump, 3 bar mains pressure on a 15mm/lead water main. Downstream pipework was all 22mm

You could do what we have done in the past and install an unvented cylinder without an accumulator, but with provision to add one in later. It works out a bit more expensive if you do split the job up, but you do have that chance of not needing the exra work.

However, if your incoming mains is only 14 litre a minute, and you have decent pressure. It might be worth investigating upgrading your water main first.

 

[hard-work]

How long did it take to recharge the accumulator?

 

[Dan Robinson]

About 45 minutes IIRC.