Questions about putting a pump on a gravity feed hot water supply

[kevin12345]

Thanks for the reply, I understand the point about the dedicated feed but I was thinking of putting the pump on the hot outlet that feed the whole house because it is only a 1 bedroom house and only one person living there so having more then one outlet on at a time would be very unlikely. Does the fact that combination cylinders have an internal vent do away with the problem about sucking Air into the pump, hence not needing a surrey or Essex flange?
Thanks

 

[Madrab]

The air bubbles rise to the top when the water is heated and are usually expelled via the vent. Can you see where your supply pipe exits the cylinder? Is it around 50/100mm below the top?

The only other issue you may have here is capacity, you will need to be careful that the cold water cistern can deliver enough water to the HW cylinder when pumping to a shower for any length of time, adequate supply needed (at least 22mm full flow) to the cistern & very careful pump selection. The small in line pump that was linked to earlier may be worth a thought depending on it's throughput.

 

[kevin12345]

Here is a photo of where the pipes are.
The hot outlet is 22mm, comes out of side of cylinder, near the top at least 100mm below top I would say ( Sorry, I'm not at home to measure it exactly right now), as you can see it is hard to get to the outlet. Cold feed to cistern is 15mm main feed but it is quite high pressure I think ( It only takes just under 3 seconds to fill a litre jug at the Bath tap cold outlet which is also mains feed).
Combination cylinder is 210 litre Hot and 45 litre cold cistern.
Your opinion on this type of situation is very appreciated.
Thanks

 

[OvertonPlumber]

Best you could do is fit a little ct55 and pump bath taps/shower. You are going to have to limit to yourself to short shower. Pump wont last long couple of years at most. Pump wont be guaranteed as you cannot fit it legally to thqt setup.

 

[Madrab]

as you cannot fit it legally to thqt setup

Don't believe it's actually illegal to fit a pump to a fortic setup?? It's just not a good idea, nor recommended as it can be run dry pretty quickly. If it runs dry and the pump is stuffed because of it then for sure the warranty will not be honoured.

Ideally a large separate cold cistern to a standard cylinder would be used or switch to a different setup (unvented etc). If the setup cannot be changed then a more clever way to use the current system should be looked into.

 

[kevin12345]

Not sure what yo do as the house is housing association, they have said ok to changing the bath mixer taps to a bath/shower mixer and yes to pumping hot water but it's getting more challenging then I thought. Double checked hot tank and that is 144 litres with a 40 litre cold tank. Starting to wonder if may be putting in an electric shower may be a better option. What do you think?

 

[Madrab]

An electric shower is one alternative and the Mira's are ok but again, not the best for pressure, especially in the winter, when output drops a 1.3rd. That coupled with the expense of a new, suitably sized power circuit you would need to run it, depending on the length of cable run.

Are you in a flat, is the cylinder in a middle cupboard? Could a larger cold cistern be installed above if the fortic cylinder was removed and a standard cylinder installed? I think you want to get someone in to look at the system and see what possible solutions could be found.

Mains HW is your ideal but that's pricey to install.

 

[kevin12345]

Thanks for reply. Its a 1 bed house, it does have a loft but as I have mentioned it is a housing Association property. The house is all electric and although the Housing people have given permission for a shower I don't think they would be very happy about changing the economy 7 tank and putting another cold cistern in the Loft.
Trying to find info on electric showers. Can you take mains cold feed that goes to the Bath taps and tee under the Bath in 15mm to feed an electric Shower?
What kind of money would I be looking at to get it wired in by electrician and signed off with certificate?
Thanks

 

[Madrab]

yes, the cold mains to the bath could be used to tee up to the shower.

As far as the leccy part then you're in the wrong forum I'm afraid. It all really depends on if you have capacity in the consumer unit, size of cable, length of run, how difficult to fit etc.