Unvented hot water system and new shower

[wwwebber]

Apologies, title should have read "Vented ...."

Hi, we're intending to eventually install a unvented hot water system to run one or more showers directly. The current shower is a pathetic electric 9kw which we both hate with a passion as the flow & heat is no good and our previous property was fed via a combi boiler.

However, we cant install a unvented hot water system for a year or two whilst we carry out other works (and save up !!) so we want a quick fix. We also now have a system boiler.

So, how does this sound ? :-

In our en-suite we have room in one corner to install a new tray / cubicle, hot & cold piping already exists nearby. Our mains pressure is pretty good apparently so can we not simply run the hot & cold water supply directly to a thermostatic mixer in this new cubicle ?. Remember this is not permanent but could give us a much better shower for the period that we need it ?

Thank you.

 

[fezster]

So at the moment you have a vented HW cylinder which is gravity fed from a cold water storage tank? The problem you'll have is that the pressure from this system will be very low, regardless of your incoming supply pressure.

You could fit a pump in the interim to both the gravity fed hot and cold (to give your new thermostatic shower a balanced supply) which could then eventually be replaced by mains fed hot and cold with an unvented cylinder.

 

[wwwebber]

@fezster

Thank you for your reply. Just been thinking more about the future unvented system - the feed into my house is only 15mm which apparently could be a problem. If we have to stay with a vented system and I were to install another shower in the main bathroom - would this need an additional pump ?. Thanks again.

 

[fezster]

Depends on the type of pump. You can get "whole house" pumps, but my experience has only been with shower pumps - in which case you'd require one for each bathroom. You need to be careful you have enough water storage capacity to facilitate two pumps being used simultaneously.

I wouldn't assume a 15mm pipe is inadequate for an unvented cylinder. You need to measure the pressure and flow rate.

 

[wwwebber]

@fezster

Brilliant - I'll get pressure & flow rate measured and if it is inadequate I'll look into putting in a couple of pumps instead on a permanent basis. However, again thinking about this more, just putting in a couple of pumps sounds a hell of a lot cheaper than putting in a new unvented system. Maybe I should stick with vented if the pumps sort out the flow rate etc. And yes, would need to ensure the vented cylinder is big enough to tackle two showers at the same time if not then common sense should prevail.

Good stuff - thanks.

 

[wwwebber]

Another question - hopefully not too dumb !! :-

Can I converted the central heating to a sealed system and keep the vented system for hot water ?. I apparently need to move to a sealed system if we want rads in the loft rooms which is where the cistern & f/e tanks are.

Thanks.

 

[fezster]

But won't your cold water storage tank be in the loft also?

I don't believe there's any issue with running a sealed CH system with a vented HW tank. Remember you'll need an expansion vessel added to accommodate hot water expansion in the CH.

 

[Mottie]

We’ve just got a 15mm mains feed to our house. We had a gravity fed shower in the bathroom with about a 1.5m head. It was okay although it was fed in 22mm pipe. We had our system converted to sealed with an unvented cylinder earlier this year. The difference is very noticeable.

 

[Dan Robinson]

Another question - hopefully not too dumb !! :-

Can I converted the central heating to a sealed system and keep the vented system for hot water ?. I apparently need to move to a sealed system if we want rads in the loft rooms which is where the cistern & f/e tanks are.

Thanks.

If the boiler is suitable then the only issue is, if the cylinder is old, the coil might not look take the pressure and you'll end up needing a new one anyway.

 

[wwwebber]

But won't your cold water storage tank be in the loft also?

Yes, its about 3 foot higher than the f/e tank.

I don't believe there's any issue with running a sealed CH system with a vented HW tank. Remember you'll need an expansion vessel added to accommodate hot water expansion in the CH.

Great - thank you.

 

[wwwebber]

If the boiler is suitable then the only issue is, if the cylinder is old, the coil might not look take the pressure and you'll end up needing a new one anyway.

Yes, need to check the boiler is suitable, it's inside an Aga like gas stove but apparently only about 12 years old. Yes, may need a larger capacity cylinder anyway if we want to run 2 showers at the same time etc but crucially still much cheaper than a new unvented hot water system.