venturi or single pump

[showernob]

i can't find an exact answer to this so apologies if I'm covering old ground..

I've fitted a new bathroom and of course the last part of teh installation is the shower unit.

My house has a normal vented system - Y-type. The shower has about 2-3ft of positive head. The water in to the bathroom is a 15mm cold and 22mm hot from the tank which I've tee'd off to the bath taps and used swept bends rather than elbows until the final shower inputs. The hot water feed is reduced however to 15 mm after teh bath for the final stretch as teh inputs to my thermostatic shower unit are both 15mm. All pipes have been boxed in and tiled over.

So far so good, I think (I am an amateur after all).

I had intended to install a single impeller pump under the end of the bath as I already have a suitable electric feed which used to serve an old electric shower. reasoning for putting it under the end of the bath is that the airing cupboard is in my daughter's bedroom and I don't want it to disturb her. The pump is on order.

Now, however, I've just found out about Venturi showers which seem to be an even better solution on the surface.

The New Team Jet Stream venturi type shower looks good, but requires a 22mm hot feed according to teh instructuions I've found on line. Am I going to get the benefit from my already reduced 15 mm hot feed or will it end up a false economy?

The Trevi Boost looks even better but, having already routed my pipework I think it would be too massive a job to get the pipework to fit.

I've also seen on other forums that I may have problems with my original solution?

 

[Jake1886]

Have you run a independent hot supply from your hot water cylinder for the shower installation?

 

[showernob]

No. It's the original 22mm feed which originally only supplied the bath.

 

[Jake1886]

So you still have a bath in place you have tee'd off the supply to the taps for the shower? If you have done that then its not correct. The venturi shower will need its own independent hot supply from the cylinder (22mm), so surrey flange or essex boss. You can tee off the hot supply local to the cylinder but not great. It'll also need a 'mains' cold water feed, this is what gives you the pressure boost. Don't forget to fit check valves, only need to be single check.

If your fitting a pump or a power shower you again need independent supplies from your cylinder and cws cistern.

 

[showernob]

The tee'd off supply is to the bath taps, not the shower. not sure if that makes a difference? OK, so i can get a surrey flange in the top of my tank and make that my dedicated bathroom supply, but will it still be ok to tee-off for the bath taps? Considering they won't be used at the same time.

 

[Jake1886]

Cap off the tee's you cut in on your bath supplies and leave them to feed the bath. If the cold feed to your bath tap is fed via the mains then you could still use that as a cold supply to the venturi shower. If the supply is fed via a down service (tank fed) then you can't use that and continue to cap off.

Run a independent hot supply from the cylinder to feed only your shower or pump.

If your opting to use the venturi shower then you need to run a cold supply from the mains cold water service. You can't use a down service, it simply wouldn't work.

If you are using a pump or a power shower then you need to holesaw a boss in your cold water storage cistern and use that as your independent shower cold feed.

Hope that helps.

 

[showernob]

can I get round the cold water pipe by fitting a prv?

 

[Jake1886]

can I get round the cold water pipe by fitting a prv?

What's that going to achieve mate?

 

[Charnwood]

Whilst venturi showers are a good idea per se, they are not very versatile;

Not thermostatic
Dificult to control flow
Can only be used with a single mode handset.

Last resort IMHO.

 

[Hufty]

Have you run a independent hot supply from your hot water cylinder for the shower installation?

No. It's the original 22mm feed which originally only supplied the bath.

I would have thought this is OK. The reason you're meant to have a separate feed is if the hot pipe also fed the kitchen sink, say, you might get temperature fluctuations if someone did the washing up whilst you were showering. You're unlikely to let someone run a bath whilst you're stood in there having a shower.

 

[Jake1886]

They are talking about fitting a venturi type shower which is not thermostatic. I'm sure the manu would recommend its own supply, or at least teeing off in the airing cupboard so its the first draw off.

They were also talking about fitting a pump. That would need its own supply because of air ingress etc.

 

[showernob]

Would I have a problem with air ingress? the pump would be at a lower level than the bath taps and shower.

Jake: the point of fitting a PRV to the cold feed - to reduce the incoming mains pressure - thus doing away with the need to put a tank fed cold water feed in? (wishful thinking?)

And this all got me thinking - I just assumed the cold water feed to the bathw as mains fed. What's the best way to tell? I know that if I turn the stopcock the cold water stops immediately. I guess if it was tank-fed it would only stop when the tank empties.

I've answered my own question again, haven't I?

 

[showernob]

Have you run a independent hot supply from your hot water cylinder for the shower installation?

No. It's the original 22mm feed which originally only supplied the bath.

I would have thought this is OK. The reason you're meant to have a separate feed is if the hot pipe also fed the kitchen sink, say, you might get temperature fluctuations if someone did the washing up whilst you were showering. You're unlikely to let someone run a bath whilst you're stood in there having a shower.

My wife doesn't do enough washing up for this to be a problem!

 

[Jake1886]

Would I have a problem with air ingress? the pump would be at a lower level than the bath taps and shower.

Shower Pump will need its own cold water supply from 'cold storage tank' and its own hot supply from cylinder. I wouldn't recommend doing it any other way.

Jake: the point of fitting a PRV to the cold feed - to reduce the incoming mains pressure - thus doing away with the need to put a tank fed cold water feed in? (wishful thinking?)

If your cold water main is 3bar or above then you'll need to fit a prv for a venturi shower.

And this all got me thinking - I just assumed the cold water feed to the bathw as mains fed. What's the best way to tell? I know that if I turn the stopcock the cold water stops immediately. I guess if it was tank-fed it would only stop when the tank empties.

I've answered my own question again, haven't I?

Yep

I think you need to decide what you want to fit, be it a mixer shower with a pump, a venturi type shower, a power shower etc. And then go from there. Should really have thought about this before starting imho.

 

[showernob]

I started out with the thermostatic bar which is still my pteferred option tbh. besides, I've bought all the gear!