Unvented undersink water heater

[Observer]

I want to provide H&C water to a small sink in a garden toilet. I have identified the Redring MS6 undersink unvented water heater and want to double-check my interpretation of manufacturer's instructions (MI) as to whether an expansion tank and associated fittings is mandated or can be omitted.

The water supply from the main house will enter at one end of the building underground and the first draw off will be a WC cistern. Then there will the be a run of ~2m to a location below a basin where I want to install the heater to feed a mixer tap on the basin. A cold water feed will be needed as well, of course.

According to MI, an expansion tank is required if the pipe from the heater back to the "nearest cold water draw-off" is <1.7m. In the set up described above, the cold supply to the basin mixer tap willl < 0.5m from the heater, so it appears an expansion tank is needed. However, if the cold feed immediately downstream of the WC cistern is split so that the water heater and the cold feed for the basin have separate runs, I can meet the minimum 1.7m stipulation?

Does this idea work?

https://www.redring.co.uk/sites/default/files/assets//MS6 booklet New 2018.pdf

 

[Madrab]

As long as the closest tee which is on the same supply pipe as the heater, whether it is to the WC or off to the basin, is >1.7m then that will meet the MI requirements.

 

[ianmcd]

yes that should be fine, it is important with this unit that the sacrificial anode is checked at the minimum yearly, dont forget to have it done

 

[Observer]

yes that should be fine, it is important with this unit that the sacrificial anode is checked at the minimum yearly, dont forget to have it done

Thanks both. What does the anode check test for and is there really any reason it can't be DIY (I know the MI says "qualified technician" but...). I assume remove, clean with wire brush, replace if 50% or more worn?

 

[ianmcd]

Thanks both. What does the anode check test for and is there really any reason it can't be DIY (I know the MI says "qualified technician" but...). I assume remove, clean with wire brush, replace if 50% or more worn?

I have about 30 Andrews unvented cylinders that I service every year and to service the Anode you remove it and measure it, if less than 300mm left of the Anode it is replaced, some can be checked with a multimeter, sorry I dont know the specifications for that heater but google is your friend there, you will find it somewhere, you will be surprised at the rate they erode

 

[draineal]

We use ECOTOUCH ECO55, a water heater for the shower and sink in the bathroom and a separate one for the laundry room and kitchen. This electric tankless water heater works very well.

 

[Madrab]

We use ECOTOUCH ECO55, a water heater for the shower and sink in the bathroom and a separate one for the laundry room and kitchen. This electric tankless water heater works very well.

As per the forum rules .... please don't resurrect old posts.

Please also note that this is a UK forum, the equipment you reference is more for the US market I believe?