Feed for shower pump

[FEP]

Hello.

I want to fit a new shower over my bath. The hot water pressure is not great so I reckon I'll need a shower pump.

So far so good, but the hot water feed from the immersion tank (cupboard in the living room!) is the other side of the hallway from the bathroom - its a solid floor and the current run from immersion to bathroom hot taps is over the top in the ceiling and very hard to get to. I live in a flat - 4th floor of 4. I have no access to the roof void.

What I wanted to do was tee off from the bath tap feed for the pump, but reading about surrey flanges, I'm getting the impression that I can't do that.

What goes wrong if I do? Is it essential that I take a direct feed from the immersion?

Thanks for your help.

FEP

 

[Madrab]

You need to fit a flange on the top of the cylinder or cut a separate feed into the cylinder below the top. One of the enemies of water pumps is air. When the water in the cylinder is heated it releases trapped air in the form of bubbles, if you pump is connected to the feed that is from the top of the cylinder it can draw that air in and cause problems with the pump - (noise, temp/flow fluctuations, premature wear, pump failure). A surrey flange has a dip tube and 2 feed outlets. The dip tube drops down into the cylinder taking water from below the top of the tank just for the pump, therefore minimising the chance of air being drawn in.
Fitting a power shower that has a internal pump may be an option as they can feed of the normal hot and cold pipes as long as there is sufficient head of water to it but depending on the draw capacity of the pump, it may be affected when other taps on the same pipework are used.

Ideally power showers or pumps need dedicated hot and cold feeds to work effectively.

 

[duffin]

or alternatively you could fit a pump the hot water for all of your flat, solving the shower problem and boosting the rest of your outlets too.

 

[FEP]

Thanks for that.

What is so special about the pump in a power shower that means it can run of a non dedicated feed, whilst a shower pump can't?

 

[Fluffster]

The internal pump on so called power showers are not as powerful as a seperate twin impellor pump.

Pete

 

[Madrab]

you can sometimes get away with a 'on the wall' power shower connected into the normal domestic water feed if the feed pipes are 22mm and only reduced at the outlet as they are smaller and don't have the same draw that a large shower pump has but it can still be affected by air bubbles and definitely by outlets that are opened if prior to it on the pipe so not ideal, especially if the shower head is just below the cold water tank. (You need to gauge where the shower head is going to be in relation to the cold water tank in deciding if you will have a positive/negative or neutral head of water) This is critical as to what type of pumped system you can have)
A stand alone pump is much more powerful & requires an uninterrupted supply as it has a larger capacity and is badly affected/damaged by air and the opening of taps prior to the pump feed. Saw a DIY'd under a bath just for a shower which was drawing in air through the sink tap because the flow rate of the pipework was exceeded by the draw of the pump and it was last in the line.
Again...to have a fault free installation that won't give you problems a dedicated feed for either is recommended and insisted on for a stand alone pump.
Another option that is often overlooked is what's called a venturi system, it uses cold mains pressure to draw out low pressure hot water, they used to be terrible and fluctuations in temp and flow were common but it looks like the technology is catching up and are more acceptable these days. They're not power showers though.

 

[FEP]

or alternatively you could fit a pump the hot water for all of your flat, solving the shower problem and boosting the rest of your outlets too.

That's an interesting idea. How would that work - in line in the immersion outlet - potentially with a surrey flange, and then draw the feed for the mixer of the bath tap inlet with no need to run extra pipes over the hall corridor?